Remove stale staging apps (#19034)

* Add a script to remove stale staging apps
* Add a workflow to remove stale staging apps on a regular basis

.github/workflows/remove-stale-staging-apps.yml

@@ -0,0 +1,29 @@
+name: Remove stale staging apps
+
+# **What it does**:
+# This cleans up any rogue staging applications that outlasted the closure of
+# their corresponding pull requests.
+# **Why we have it**:
+# Staging applications sometimes fail to be destroyed when their corresponding
+# pull request is closed or merged.
+# **Who does it impact**:
+# Anyone with a closed, spammy, or deleted pull request in docs or docs-internal.
+
+on:
+  schedule:
+    - cron: '15,45 * * * *' # every thirty minutes at :15 and :45
+
+jobs:
+  remove_stale_staging_apps:
+    name: Remove stale staging apps
+    if: ${{ github.repository == 'github/docs-internal' }}
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@5a4ac9002d0be2fb38bd78e4b4dbde5606d7042f
+      - name: npm ci
+        run: npm ci
+      - name: Run script
+        run: script/remove-stale-staging-apps.js
+        env:
+          HEROKU_API_TOKEN: ${{ secrets.HEROKU_API_TOKEN }}
+          GITHUB_TOKEN: ${{ secrets.DOCUBOT_FR_PROJECT_BOARD_WORKFLOWS_REPO_ORG_READ_SCOPES }}