Add stale bot (#698)

.github/workflows/stale.yml

@@ -0,0 +1,28 @@
+name: 'stale'
+
+on:
+  schedule:
+    - cron: "0 8 * * *"
+
+jobs:
+  stale:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/stale@v9
+        with:
+          # Issues
+          days-before-issue-stale: 60
+          stale-issue-message:
+            "This issue is stale because it has been open for 60 days with no activity.
+            What is the action to take here?"
+          days-before-issue-close: -1
+
+          # Pull requests
+          delete-branch: true
+          days-before-pr-stale: 30
+          stale-pr-message:
+            "This PR is stale because it has been open for 45 days with no activity. Remove
+            the `stale` label or comment or this will be closed in 30 days."
+          days-before-pr-close: 30
+          close-pr-message:
+            "This PR was closed because it has been marked stale for 30 days with no activity."