[CI] Close stale pull requests (learning-process#296)

Author: aobolensk

.github/workflows/nightly.yml

@@ -0,0 +1,23 @@
+name: Nightly routine
+
+on:
+  schedule:
+    - cron: '0 0 * * *'
+
+permissions:
+  issues: write
+  pull-requests: write
+
+jobs:
+  close-stale-prs:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/stale@v9
+        with:
+          stale-pr-message: 'This pull request is stale for 2 weeks and is going to be closed'
+          days-before-pr-stale: 14
+          days-before-issue-stale: -1
+          days-before-pr-close: 14
+          days-before-issue-close: -1
+          stale-pr-label: 'stale'
+          operations-per-run: 100