Add workflow for closing stale issues and PRs (kubeflow#2073)

* Add workflow for closing staled issues and PRs

Signed-off-by: Yi Chen <github@chenyicn.net>

* Add job permissions

Signed-off-by: Yi Chen <github@chenyicn.net>

---------

Signed-off-by: Yi Chen <github@chenyicn.net>

.github/workflows/stale.yaml

@@ -0,0 +1,35 @@
+name: Close stale issues and PRs
+
+on:
+  schedule:
+    - cron: "0 1 * * *"
+
+jobs:
+  stale:
+    runs-on: ubuntu-latest
+
+    permissions:
+      issues: write
+      pull-requests: write
+
+    steps:
+      - uses: actions/stale@v9
+        with:
+          days-before-issue-stale: 60
+          days-before-issue-close: 30
+          days-before-pr-stale: 60
+          days-before-pr-close: 30
+          stale-issue-message: >
+            This issue has been automatically marked as stale because it has been open 60 days with no activity.
+            Remove stale label or comment or this will be closed in 30 days.
+            Thank you for your contributions.
+          close-issue-message: >
+            This issue has been automatically closed because it has been stalled for 30 days with no activity.
+            Please comment "/reopen" to reopen it.
+          stale-pr-message: >
+            This pull request has been automatically marked as stale because it has been open 60 days with no activity.
+            Remove stale label or comment or this will be closed in 30 days.
+            Thank you for your contributions.
+          close-pr-message: >
+            This pull request has been automatically closed because it has been stalled for 30 days with no activity.
+            Please comment "/reopen" to reopen it.