Added inactivity action

Author: JHubi1

.github/workflows/inactivity.yaml

@@ -0,0 +1,18 @@
+name: Close inactive issues
+on:
+  schedule:
+    - cron: "30 1 * * *"
+
+jobs:
+  close-issues:
+    runs-on: ubuntu-latest
+    permissions:
+      issues: write
+      pull-requests: write
+    steps:
+      - uses: actions/stale@v5
+        with:
+          days-before-stale: -1
+          days-before-pr-close: -1
+          days-before-issue-close: 21
+          close-issue-message: "This issue was closed because it has been inactive for 21 days. Reopen it or create a new issue in case the problem still persists."