ci: add actions/stale workflow to close stale issues

.github/workflows/Stale.yml

@@ -0,0 +1,29 @@
+name: Close stale issues
+on:
+  schedule:
+    - cron: "30 1 * * *"
+  workflow_dispatch:
+permissions:
+  issues: write
+  pull-requests: write
+jobs:
+  stale:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/stale@v11
+        with:
+          # Issues: mark stale after 60 days without activity, close 7 days later (action defaults).
+          days-before-issue-stale: 60
+          days-before-issue-close: 7
+          stale-issue-label: stale
+          stale-issue-message: >
+            This issue has been automatically marked as stale because it has had no
+            activity in the last 60 days. It will be closed in 7 days if no further
+            activity occurs. Comment or remove the `stale` label to keep it open.
+          close-issue-message: >
+            Closing this issue because it has been stale for 7 days with no further
+            activity. Feel free to reopen it if it is still relevant.
+          exempt-issue-labels: pinned,security
+          # Pull requests are left alone.
+          days-before-pr-stale: -1
+          days-before-pr-close: -1