added stale action, running twice a day

.github/workflows/stale.yml

@@ -0,0 +1,19 @@
+name: 'Stale issues & PRs'
+on:
+  schedule:
+    - cron: '27 0,12 * * *'
+
+jobs:
+  stale:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/stale@v9
+        with:
+          days-before-stale: 7
+          days-before-pr-stale: 2
+          days-before-close: 3
+          stale-issue-message: 'This issue has been marked as stale, and will be automatically closed in 3 days.'
+          stale-pr-message: 'This PR has been marked as stale, and will be automatically closed in 3 days.'
+          close-issue-message: 'Closing issue as it has been marked as stale for 3 days.'
+          close-pr-message: 'Closing PR as it has been marked as stale for 3 days.'
+          exempt-all-milestones: true