Add stalebot for issues

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

@@ -0,0 +1,31 @@
+name: 'Close stale issues'
+on:
+  schedule:
+    - cron: '30 1 * * *'
+  workflow_dispatch:
+
+permissions:
+  issues: write
+
+jobs:
+  stale:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/stale@v8
+        with:
+          stale-issue-message: >
+            This issue has automatically been marked as _stale_ because it has not had
+            any activity in the last 50 days. You can _unstale_ it by commenting or
+            removing the label. Otherwise, this issue will be closed in 10 days.
+          stale-pr-message: >
+            This pull request has automatically been marked as _stale_ because it has
+            not had any activity in the last 50 days. You can _unstale_ it by commenting
+            or removing the label.
+          close-issue-message: >
+            This issue was closed automatically because it has been stale for 10 days
+            with no activity.
+          days-before-stale: 50
+          days-before-close: 10
+          # Do not affect pull requests:
+          days-before-pr-stale: -1
+          days-before-pr-close: -1