Add "stale" action to help manage issues and pull requests

.github/workflows/stale.yml

@@ -0,0 +1,41 @@
+name: Mark stale issues and pull requests
+
+on:
+  schedule:
+    - cron: '30 1 * * *'
+  workflow_dispatch:
+
+permissions:
+  issues: write
+  pull-requests: write
+
+jobs:
+  stale:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/stale@v9
+        with:
+          stale-issue-label: 'stale'
+          stale-pr-label: 'stale'
+          exempt-issue-labels: 'good first issue,Design Proposal,in-progress'
+          exempt-pr-labels: 'in-progress'
+
+          days-before-issue-stale: 60
+          days-before-issue-close: 14
+          days-before-pr-stale: 90
+          days-before-pr-close: 14
+
+          close-issue-reason: 'not_planned'
+
+          stale-issue-message: >
+            This issue has been automatically marked as stale because it has not had
+            recent activity. It will be closed in 14 days if no further activity occurs.
+            If this is still relevant, please comment to keep it open.
+          stale-pr-message: >
+            This pull request has been automatically marked as stale because it has not had
+            recent activity. It will be closed in 14 days if no further activity occurs.
+            If this is still active work, please comment or push a new commit to keep it open.
+          close-issue-message: >
+            Closing due to inactivity. If this is still relevant, please reopen or file a new issue.
+          close-pr-message: >
+            Closing due to inactivity. Feel free to reopen if you'd like to continue this work.