Add stale bot in github workflow (#246)

* add stale bot

* use https://github.com/marketplace/actions/close-stale-issues instead

.github/workflows/stale.yml

@@ -0,0 +1,34 @@
+name: 'Close stale issues and PRs'
+on:
+  schedule:
+    - cron: '30 1 * * *'
+
+jobs:
+  stale:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/stale@v4
+        with:
+          days-before-stale: 30
+          days-before-close: 7
+          stale-issue-message: >
+            This issue has been automatically marked as stale because it has not had
+            recent activity in the last 30 days. It will be closed in the next 7 days unless it is tagged (pinned, good first issue or help wanted) or other activity occurs. Thank you
+            for your contributions.
+          close-issue-message: >
+            This issue has been automatically closed because it has not had activity in the
+            last 37 days. If this issue is still valid, please ping a maintainer and ask them to label it as pinned, good first issue or help wanted.
+            Thank you for your contributions.
+          stale-pr-message: >
+            This pull request has been automatically marked as stale because it has not had
+            activity in the last 30 days. It will be closed in 7 days if no further activity occurs. Please
+            feel free to give a status update now, ping for review, or re-open when it's ready.
+            Thank you for your contributions!
+          close-pr-message: >
+            This pull request has been automatically closed because it has not had
+            activity in the last 37 days. Please feel free to give a status update now, ping for review, or re-open when it's ready.
+            Thank you for your contributions!
+          stale-issue-label: 'stale'
+          exempt-issue-labels: 'pinned,good first issue,help wanted'
+          stale-pr-label: 'stale'
+          exempt-pr-labels: 'pinned'