Add demo add-on for adding a custom exporter

demos/add_exporter/__init__.py

@@ -0,0 +1,15 @@
+"""
+An example of adding an exporter to export page.
+"""
+
+from pathlib import Path
+
+from aqt import gui_hooks
+from aqt.webview import AnkiWebView
+
+
+def setup(webview: AnkiWebView) -> None:
+    webview.eval(Path(__file__).with_name("init.js").read_text(encoding="utf8"))
+
+
+gui_hooks.webview_did_inject_style_into_page.append(setup)

demos/add_exporter/init.js

@@ -0,0 +1,27 @@
+function updateExporters(exporters) {
+    for (const exporter of exporters) {
+        exporter.isDefault = false;
+    }
+    exporters.push({
+        extension: "csv",
+        label: "My fancy CSV",
+        showDeckList: true,
+        showIncludeScheduling: false,
+        showIncludeDeckConfigs: false,
+        showIncludeMedia: false,
+        showIncludeTags: false,
+        showIncludeHtml: false,
+        showLegacySupport: false,
+        showIncludeDeck: false,
+        showIncludeNotetype: false,
+        showIncludeGuid: false,
+        isDefault: true,
+        doExport: (outPath, limit, options) => {
+            alert("Not implemented!");
+            return Promise.resolve();
+        }
+    });
+    return exporters;
+}
+
+requireAsync("anki/ExportPage").then(mod => mod.exporters.update(updateExporters));