ci: Add action to close stale PRs and issues (#2388)

Co-authored-by: mergify[bot] <37929162+mergify[bot]@users.noreply.github.com>

.github/workflows/close-stale.yml

+name: 'Close stale issues and PRs'
+on:
+  schedule:
+    - cron: '30 1 * * *'
+
+jobs:
+  stale:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/stale@v4
+        with:
+          stale-pr-message: 'This PR is stale because it has been open 14 days with no activity. Remove stale label or comment or this will be closed in 5 days.'
+          exempt-pr-labels: exempt-stale
+          days-before-issue-stale: 999
+          dats-before-pr-stale: 14
+          days-before-close: 5
+          repo-token: ${{ secrets.GITHUB_TOKEN }}
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