Add Example App (#64)

### Description

- Adds an example app. Just a barebones example of how to use the `TextView` class to create a plain-text editor.
- The project is set up so the package is a local, editable, dependency.

This has been extremely useful in CESE, and should help when developing this package. It's also good documentation, and we can point people towards this example app if they'd like to see how to use the text view.

### Related Issues

- N/A

### Checklist

- [x] I read and understood the [contributing guide](https://github.com/CodeEditApp/CodeEdit/blob/main/CONTRIBUTING.md) as well as the [code of conduct](https://github.com/CodeEditApp/CodeEdit/blob/main/CODE_OF_CONDUCT.md)
- [x] The issues this PR addresses are related to each other
- [x] My changes generate no new warnings
- [x] My code builds and runs on my machine
- [x] My changes are all related to the related issue above
- [x] I documented my code

### Screenshots

![Screenshot 2025-01-09 at 3 06 14 PM](https://github.com/user-attachments/assets/bc94e85d-eada-4dd0-9337-133cd79ede9e)

Example/CodeEditTextViewExample/CodeEditTextViewExample.xcodeproj/project.xcworkspace/xcshareddata/swiftpm/Package.resolved

@@ -0,0 +1,41 @@
+{
+  "pins" : [
+    {
+      "identity" : "rearrange",
+      "kind" : "remoteSourceControl",
+      "location" : "https://github.com/ChimeHQ/Rearrange",
+      "state" : {
+        "revision" : "5ff7f3363f7a08f77e0d761e38e6add31c2136e1",
+        "version" : "1.8.1"
+      }
+    },
+    {
+      "identity" : "swift-collections",
+      "kind" : "remoteSourceControl",
+      "location" : "https://github.com/apple/swift-collections.git",
+      "state" : {
+        "revision" : "671108c96644956dddcd89dd59c203dcdb36cec7",
+        "version" : "1.1.4"
+      }
+    },
+    {
+      "identity" : "swiftlintplugin",
+      "kind" : "remoteSourceControl",
+      "location" : "https://github.com/lukepistrol/SwiftLintPlugin",
+      "state" : {
+        "revision" : "87454f5c9ff4d644086aec2a0df1ffba678e7f3c",
+        "version" : "0.57.1"
+      }
+    },
+    {
+      "identity" : "textstory",
+      "kind" : "remoteSourceControl",
+      "location" : "https://github.com/ChimeHQ/TextStory",
+      "state" : {
+        "revision" : "8dc9148b46fcf93b08ea9d4ef9bdb5e4f700e008",
+        "version" : "0.9.0"
+      }
+    }
+  ],
+  "version" : 2
+}

Example/CodeEditTextViewExample/CodeEditTextViewExample/Assets.xcassets/AccentColor.colorset/Contents.json

@@ -0,0 +1,11 @@
+{
+  "colors" : [
+    {
+      "idiom" : "universal"
+    }
+  ],
+  "info" : {
+    "author" : "xcode",
+    "version" : 1
+  }
+}

Example/CodeEditTextViewExample/CodeEditTextViewExample/Assets.xcassets/AppIcon.appiconset/Contents.json

@@ -0,0 +1,35 @@
+{
+  "images" : [
+    {
+      "idiom" : "universal",
+      "platform" : "ios",
+      "size" : "1024x1024"
+    },
+    {
+      "appearances" : [
+        {
+          "appearance" : "luminosity",
+          "value" : "dark"
+        }
+      ],
+      "idiom" : "universal",
+      "platform" : "ios",
+      "size" : "1024x1024"
+    },
+    {
+      "appearances" : [
+        {
+          "appearance" : "luminosity",
+          "value" : "tinted"
+        }
+      ],
+      "idiom" : "universal",
+      "platform" : "ios",
+      "size" : "1024x1024"
+    }
+  ],
+  "info" : {
+    "author" : "xcode",
+    "version" : 1
+  }
+}

Example/CodeEditTextViewExample/CodeEditTextViewExample/Assets.xcassets/Contents.json

@@ -0,0 +1,6 @@
+{
+  "info" : {
+    "author" : "xcode",
+    "version" : 1
+  }
+}

Example/CodeEditTextViewExample/CodeEditTextViewExample/CodeEditTextViewExample.entitlements

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+<?xml version="1.0" encoding="UTF-8"?>
+<!DOCTYPE plist PUBLIC "-//Apple//DTD PLIST 1.0//EN" "http://www.apple.com/DTDs/PropertyList-1.0.dtd">
+<plist version="1.0">
+<dict>
+	<key>com.apple.security.app-sandbox</key>
+	<true/>
+	<key>com.apple.security.files.user-selected.read-write</key>
+	<true/>
+</dict>
+</plist>

Example/CodeEditTextViewExample/CodeEditTextViewExample/CodeEditTextViewExampleApp.swift

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+//
+//  CodeEditTextViewExampleApp.swift
+//  CodeEditTextViewExample
+//
+//  Created by Khan Winter on 1/9/25.
+//
+
+import SwiftUI
+
+@main
+struct CodeEditTextViewExampleApp: App {
+    var body: some Scene {
+        DocumentGroup(newDocument: CodeEditTextViewExampleDocument()) { file in
+            ContentView(document: file.$document)
+        }
+    }
+}

Example/CodeEditTextViewExample/CodeEditTextViewExample/Documents/CodeEditTextViewExampleDocument.swift

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+//
+//  CodeEditTextViewExampleDocument.swift
+//  CodeEditTextViewExample
+//
+//  Created by Khan Winter on 1/9/25.
+//
+
+import SwiftUI
+import UniformTypeIdentifiers
+
+struct CodeEditTextViewExampleDocument: FileDocument {
+    var text: String
+
+    init(text: String = "") {
+        self.text = text
+    }
+
+    static var readableContentTypes: [UTType] {
+        [
+            .item
+        ]
+    }
+
+    init(configuration: ReadConfiguration) throws {
+        guard let data = configuration.file.regularFileContents else {
+            throw CocoaError(.fileReadCorruptFile)
+        }
+        text = String(decoding: data, as: UTF8.self)
+    }
+
+    func fileWrapper(configuration: WriteConfiguration) throws -> FileWrapper {
+        let data = Data(text.utf8)
+        return .init(regularFileWithContents: data)
+    }
+}

Example/CodeEditTextViewExample/CodeEditTextViewExample/Info.plist

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+<?xml version="1.0" encoding="UTF-8"?>
+<!DOCTYPE plist PUBLIC "-//Apple//DTD PLIST 1.0//EN" "http://www.apple.com/DTDs/PropertyList-1.0.dtd">
+<plist version="1.0">
+<dict>
+	<key>CFBundleDocumentTypes</key>
+	<array>
+		<dict>
+			<key>CFBundleTypeRole</key>
+			<string>Editor</string>
+			<key>LSItemContentTypes</key>
+			<array>
+				<string>com.example.plain-text</string>
+			</array>
+			<key>NSUbiquitousDocumentUserActivityType</key>
+			<string>$(PRODUCT_BUNDLE_IDENTIFIER).exampledocument</string>
+		</dict>
+	</array>
+	<key>UTImportedTypeDeclarations</key>
+	<array>
+		<dict>
+			<key>UTTypeConformsTo</key>
+			<array>
+				<string>public.plain-text</string>
+			</array>
+			<key>UTTypeDescription</key>
+			<string>Example Text</string>
+			<key>UTTypeIdentifier</key>
+			<string>com.example.plain-text</string>
+			<key>UTTypeTagSpecification</key>
+			<dict>
+				<key>public.filename-extension</key>
+				<array>
+					<string>exampletext</string>
+				</array>
+			</dict>
+		</dict>
+	</array>
+</dict>
+</plist>

Example/CodeEditTextViewExample/CodeEditTextViewExample/Views/ContentView.swift

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+//
+//  ContentView.swift
+//  CodeEditTextViewExample
+//
+//  Created by Khan Winter on 1/9/25.
+//
+
+import SwiftUI
+
+struct ContentView: View {
+    @Binding var document: CodeEditTextViewExampleDocument
+
+    var body: some View {
+        SwiftUITextView(text: $document.text)
+    }
+}
+
+#Preview {
+    ContentView(document: .constant(CodeEditTextViewExampleDocument()))
+}

Example/CodeEditTextViewExample/CodeEditTextViewExample/Views/SwiftUITextView.swift

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+//
+//  SwiftUITextView.swift
+//  CodeEditTextViewExample
+//
+//  Created by Khan Winter on 1/9/25.
+//
+
+import SwiftUI
+import AppKit
+import CodeEditTextView
+
+struct SwiftUITextView: NSViewControllerRepresentable {
+    @Binding var text: String
+
+    func makeNSViewController(context: Context) -> TextViewController {
+        let controller = TextViewController(string: text)
+        context.coordinator.controller = controller
+        return controller
+    }
+
+    func updateNSViewController(_ nsViewController: TextViewController, context: Context) {
+        // Do nothing, our binding has to be a one-way binding
+    }
+
+    func makeCoordinator() -> Coordinator {
+        Coordinator(text: $text)
+    }
+
+    @MainActor
+    public class Coordinator: NSObject {
+        weak var controller: TextViewController?
+        var text: Binding<String>
+
+        init(text: Binding<String>) {
+            self.text = text
+            super.init()
+
+            NotificationCenter.default.addObserver(
+                self,
+                selector: #selector(textViewDidChangeText(_:)),
+                name: TextView.textDidChangeNotification,
+                object: nil
+            )
+        }
+
+        @objc func textViewDidChangeText(_ notification: Notification) {
+            guard let textView = notification.object as? TextView,
+                  let controller,
+                  controller.textView === textView else {
+                return
+            }
+            text.wrappedValue = textView.string
+        }
+
+        deinit {
+            NotificationCenter.default.removeObserver(self)
+        }
+    }
+}

Example/CodeEditTextViewExample/CodeEditTextViewExample/Views/TextViewController.swift

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+//
+//  TextViewController.swift
+//  CodeEditTextViewExample
+//
+//  Created by Khan Winter on 1/9/25.
+//
+
+import AppKit
+import CodeEditTextView
+
+class TextViewController: NSViewController {
+    var scrollView: NSScrollView!
+    var textView: TextView!
+
+    init(string: String) {
+        textView = TextView(string: string)
+        super.init(nibName: nil, bundle: nil)
+    }
+
+    required init?(coder: NSCoder) {
+        fatalError("init(coder:) has not been implemented")
+    }
+
+    override func loadView() {
+        scrollView = NSScrollView()
+        textView.translatesAutoresizingMaskIntoConstraints = false
+
+        scrollView.translatesAutoresizingMaskIntoConstraints = false
+        scrollView.documentView = textView
+        scrollView.contentView.postsFrameChangedNotifications = true
+        scrollView.contentView.postsBoundsChangedNotifications = true
+        scrollView.hasVerticalScroller = true
+
+        self.view = scrollView
+
+        NSLayoutConstraint.activate([
+            scrollView.leadingAnchor.constraint(equalTo: view.leadingAnchor),
+            scrollView.trailingAnchor.constraint(equalTo: view.trailingAnchor),
+            scrollView.topAnchor.constraint(equalTo: view.topAnchor),
+            scrollView.bottomAnchor.constraint(equalTo: view.bottomAnchor)
+        ])
+
+        // Layout on scroll change
+        NotificationCenter.default.addObserver(
+            forName: NSView.frameDidChangeNotification,
+            object: scrollView.contentView,
+            queue: .main
+        ) { [weak self] _ in
+            self?.textView.updatedViewport(self?.scrollView.documentVisibleRect ?? .zero)
+        }
+
+        textView.updateFrameIfNeeded()
+    }
+
+    deinit {
+        NotificationCenter.default.removeObserver(self)
+    }
+}