[github] Add stale bot to close very old PRs

Signed-off-by: Kuzey Bilgin <kuzeybilgin@proton.me>

.github/workflows/stale.yml

@@ -0,0 +1,22 @@
+name: Close stale PRs
+on:
+  schedule:
+    - cron: "0 0 * * *" # Runs every day at midnight
+
+jobs:
+  stale:
+    runs-on: ubuntu-latest
+    permissions:
+      pull-requests: write
+    steps:
+      - uses: actions/stale@v9
+        with:
+          repo-token: ${{ secrets.GITHUB_TOKEN }}
+          days-before-pr-stale: 180 # 6 months before warning
+          days-before-pr-close: 365 # Closed after 12 months
+          stale-pr-label: "stale"
+          stale-pr-message: "Hi! This PR has been inactive for 6 months. If it's still relevant, please update it to let us know you’d like to keep it open 😊"
+          close-pr-message: "This PR has been automatically closed after 12 months of inactivity."
+          days-before-issue-stale: -1 # Issues are never stale
+          days-before-issue-close: -1 # Issues are never closed
+          remove-stale-when-updated: true