github: Add a workflow to close stale issues and PRs

Copied from https://github.com/cilium/cilium/blob/main/.github/workflows/close-stale-issues.yaml

Signed-off-by: Michi Mutsuzaki <[email protected]>

.github/workflows/close-stale-issues.yaml

@@ -0,0 +1,45 @@
+name: Close stale issues
+
+on:
+  schedule:
+  - cron: "30 1 * * *"
+
+permissions:
+  issues: write
+  pull-requests: write
+
+jobs:
+  stale:
+    name: Close Stale Issues
+    runs-on: ubuntu-latest
+    steps:
+    # https://github.com/marketplace/actions/close-stale-issues
+    - name: Close stale issues
+      uses: actions/stale@28ca1036281a5e5922ead5184a1bbf96e5fc984e # v9.0.0
+      with:
+        operations-per-run: 1000
+        stale-issue-label: stale
+        exempt-all-issue-assignees: true
+        exempt-issue-labels: pinned,security,good-first-issue
+
+        days-before-issue-stale: 60
+        stale-issue-message: |
+          This issue has been automatically marked as stale because it has not
+          had recent activity. It will be closed if no further activity occurs.
+        days-before-issue-close: 14
+        close-issue-message: |
+          This issue has not seen any activity since it was marked stale.
+          Closing.
+
+        stale-pr-label: stale
+        exempt-pr-labels: pinned,security,good-first-issue
+
+        days-before-pr-stale: 30
+        stale-pr-message: |
+          This pull request has been automatically marked as stale because it
+          has not had recent activity. It will be closed if no further activity
+          occurs. Thank you for your contributions.
+        days-before-pr-close: 14
+        close-pr-message: |
+          This pull request has not seen any activity since it was marked stale.
+          Closing.