Add stale.yml

.github/workflows/stale.yml

+name: Mark stale issues and pull requests
+
+on:
+  schedule:
+    - cron: "30 1 * * *"
+
+jobs:
+  stale:
+
+    runs-on: ubuntu-latest
+
+    steps:
+      - uses: actions/stale@v1
+        with:
+          repo-token: ${{ secrets.GITHUB_TOKEN }}
+          stale-issue-message: 'This issue is inactive for a long time.'
+          stale-pr-message: 'This PR is inactive for a long time'
+          stale-issue-label: 'inactive-issue'
+          stale-pr-label: 'inactive-pr'
\ No newline at end of file