improve: Added devbox.json for repeatable dev environment (#74)

First update in a long time 😅 

This PR adds a devbox.json file to make it easy to get the development environment running. 

Devbox can be found here: https://www.jetify.com/devbox

devbox.json

@@ -0,0 +1,9 @@
+{
+  "$schema": "https://raw.githubusercontent.com/jetpack-io/devbox/main/.schema/devbox.schema.json",
+  "packages": ["[email protected]"],
+  "shell": {
+    "scripts": {
+      "test": ["bundle exec rspec $@"]
+    }
+  }
+}

devbox.lock

@@ -0,0 +1,12 @@
+{
+  "lockfile_version": "1",
+  "packages": {
+    "[email protected]": {
+      "last_modified": "2021-10-22T02:15:45Z",
+      "plugin_version": "0.0.2",
+      "resolved": "github:NixOS/nixpkgs/718895c14907b60069520b6394b4dbb6e3aa9c33#ruby_2_6",
+      "source": "devbox-search",
+      "version": "2.6.8"
+    }
+  }
+}