add stalebot for issues (#226)

Co-authored-by: Kevin Yu <[email protected]>

.github/workflows/stale.yml

@@ -0,0 +1,30 @@
+name: 'Close stale issues'
+on:
+  schedule:
+    # run at 1:30 every day
+    - cron: '30 1 * * *'
+
+permissions:
+  issues: write
+
+jobs:
+  stale:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/stale@v9
+        with:
+          repo-token: ${{ secrets.GITHUB_TOKEN }}
+          # start from the oldest issues when performing stale operations
+          ascending: true
+          days-before-issue-stale: 365
+          days-before-issue-close: 30
+          stale-issue-label: stale
+          exempt-issue-labels: no stalebot,type/epic
+          stale-issue-message: >
+            This issue has been automatically marked as stale because it has not had
+            activity in the last year. It will be closed in 30 days if no further activity occurs. Please
+            feel free to leave a comment if you believe the issue is still relevant.
+            Thank you for your contributions!
+          close-issue-message: >
+            This issue has been automatically closed because it has not had any further
+            activity in the last 30 days. Thank you for your contributions!