Chore(stale): add exempt-pr-labels

Author: xjasonlyu

.github/workflows/stale.yml

@@ -17,5 +17,6 @@ jobs:
         with:
           stale-issue-message: 'This issue is stale because it has been open 60 days with no activity. Remove stale label or comment or this will be closed in 7 days'
           exempt-issue-labels: 'question,bug,enhancement,help wanted'
+          exempt-pr-labels: 'pending,WIP,help wanted'
           days-before-stale: 60
           days-before-close: 7