stale automation (#2769)

.github/workflows/stale.yml

@@ -0,0 +1,18 @@
+# Syntax: https://docs.github.com/en/actions/reference/workflow-syntax-for-github-actions
+# Github Actions Stale: https://github.com/actions/stale
+
+name: "Close stale pull requests"
+on:
+  schedule:
+    - cron: "12 3 * * *"  # arbitrary time not to DDOS GitHub
+
+jobs:
+  stale:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/stale@v4
+        with:
+          stale-pr-message: 'This PR was marked stale due to lack of activity. It will be closed in 7 days.'
+          close-pr-message: 'Closed as inactive. Feel free to reopen if this PR is still being worked on.'
+          days-before-stale: 7
+          days-before-close: 7