ci: add GitHub Action to close stale issues and PRs

- Issues/PRs inactive for 60 days are marked as stale
- Stale items are closed after 30 additional days of inactivity
- Adds appropriate warning and closing messages
- Sets daily schedule for stale checks

Signed-off-by: Sébastien Han <seb@redhat.com>

.github/workflows/stale_bot.yml

@@ -0,0 +1,45 @@
+name: Close stale issues and PRs
+
+on:
+  schedule:
+    - cron: '0 0 * * *' # every day at midnight
+
+env:
+  LC_ALL: en_US.UTF-8
+
+defaults:
+  run:
+    shell: bash
+
+permissions:
+  contents: read
+
+jobs:
+  stale:
+    permissions:
+      issues: write
+      pull-requests: write
+    runs-on: ubuntu-latest
+    steps:
+      - name: Stale Action
+        uses: actions/stale@v9
+        with:
+          stale-issue-label: 'stale'
+          stale-issue-message: >
+            This issue has been automatically marked as stale because it has not had activity within 60 days.
+            It will be automatically closed if no further activity occurs within 30 days.
+          close-issue-message: >
+            This issue has been automatically closed due to inactivity.
+            Please feel free to reopen if you feel it is still relevant!
+          days-before-issue-stale: 60
+          days-before-issue-close: 30
+          stale-pr-label: 'stale'
+          stale-pr-message: >
+            This pull request has been automatically marked as stale because it has not had activity within 60 days.
+            It will be automatically closed if no further activity occurs within 30 days.
+          close-pr-message: >
+            This pull request has been automatically closed due to inactivity.
+            Please feel free to reopen if you intend to continue working on it!
+          days-before-pr-stale: 60
+          days-before-pr-close: 30
+          operations-per-run: 300