Feature: add github stale action

.github/workflows/stale.yml

@@ -0,0 +1,19 @@
+  
+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 120 days with no activity. Remove stale label or comment or this will be closed in 5 days'
+          days-before-stale: 120
+          days-before-close: 5