ci: Add automatic cleaning on stale issues and PRs (#52)

Author: tembleking

.github/workflows/stale.yml

@@ -0,0 +1,21 @@
+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 stale because it has been open 60 days with no activity. Remove stale label or comment or this will be closed in 7 days'
+        stale-pr-message: 'This PR 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'
+        stale-issue-label: 'stale'
+        stale-pr-label: 'stale'
+        close-issue-message: 'This issue has been closed due to inactivity.'
+        close-pr-message: 'This PR has been closed due to inactivity.'