DEV: Move deprecation-finder to its own package (#60)

This will allow us to update the root package.json/lockfile like any other theme/plugin.

Also deletes the `/list_ember_deprecations.rb` script which has been superseded by `./scripts/update_ember_deprecations.rb`

.github/workflows/update-discourse-core-deprecations.yml

@@ -20,15 +20,18 @@ jobs:
         with:
           node-version: 21
 
+      - name: Set up pnpm
+        uses: pnpm/action-setup@v4
+        with:
+          package_json_file: deprecation-finder/package.json
+
       - name: pnpm install
-        run: |
-          npm install -g pnpm
-          pnpm install
+        run: pnpm -C deprecation-finder install
 
       - name: Run deprecation script
         id: run-script
         run: |
-          node ./scripts/update_discourse_core_deprecations.mjs ./discourse
+          node ./deprecation-finder/update_discourse_core_deprecations.mjs ./discourse
 
       - name: Create Pull Request
         uses: peter-evans/create-pull-request@v6

deprecation-finder/package.json

@@ -0,0 +1,18 @@
+{
+  "private": true,
+  "devDependencies": {
+    "@babel/parser": "^7.26.2",
+    "@babel/preset-env": "^7.26.0",
+    "@babel/traverse": "^7.25.9",
+    "@babel/types": "^7.26.0",
+    "content-tag": "^2.0.3",
+    "js-yaml": "^4.1.0"
+  },
+  "engines": {
+    "node": ">= 18",
+    "npm": "please-use-pnpm",
+    "yarn": "please-use-pnpm",
+    "pnpm": ">= 9"
+  },
+  "packageManager": "pnpm@9.15.5"
+}