Introduce stale workflow

.github/workflows/stale.yml

@@ -0,0 +1,28 @@
+# This workflow warns and then closes issues and PRs that have had no activity for a specified amount of time.
+#
+# You can adjust the behavior by modifying this file.
+# For more information, see:
+# https://github.com/actions/stale
+name: Mark stale issues and pull requests
+
+on:
+  schedule:
+  # Run every day at 00:00 UTC
+  - cron: '0 0 * * *'
+  # Or run on demand
+  workflow_dispatch:
+
+jobs:
+  stale:
+
+    runs-on: ubuntu-latest
+    permissions:
+      pull-requests: write
+
+    steps:
+    - uses: actions/stale@v5
+      with:
+        repo-token: ${{ secrets.GITHUB_TOKEN }}
+        days-before-pr-stale: 0
+        stale-pr-message: 'Stale pull request message'
+        stale-pr-label: 'no-pr-activity'