chore: add stale action (argoproj#1086)

Signed-off-by: Derek Wang <[email protected]>

.github/workflows/stale.yml

@@ -0,0 +1,27 @@
+name: 'Close stale issues and PRs'
+
+on:
+  schedule:
+  - cron: '21 1 * * *'
+
+jobs:
+  stale:
+    runs-on: 'ubuntu-latest'
+    steps:
+    - uses: 'actions/stale@v3'
+      with:
+        stale-issue-message: |-
+          This issue has been automatically marked as stale because it has not had
+          any activity in the last 60 days. It will be closed if no further activity 
+          occurs. Thank you for your contributions.
+        stale-issue-label: 'stale'
+        exempt-issue-labels: 'enhancement,security,pinned'
+
+        stale-pr-message: |-
+          This Pull Request is stale because it has been open for 60 days with
+          no activity. It will be closed in 7 days if no further activity.
+        stale-pr-label: 'stale'
+
+        days-before-stale: 60
+        days-before-close: 7
+