ci: Add action to lock closed PRs

.github/workflows/lock-prs.yml

@@ -0,0 +1,24 @@
+name: "Lock closed PRs"
+
+on:
+  schedule:
+  - cron: "0 */8 * * *"
+  workflow_dispatch:
+
+jobs:
+  lock:
+    runs-on: ubuntu-latest
+    steps:
+      - name: Install dependencies
+        run: sudo apt-get update && sudo apt install -y jq
+
+      - name: Lock closed PRs
+        run: |
+          cmd=$(gh pr list --repo "$REPO" -L 100 --state closed --json number,updatedAt|jq '[.[] | select(.updatedAt >= (now - (7 * 24 * 60 * 60) | todate))] | sort_by(.updatedAt) | .[] | {number: .number, updatedAt: .updatedAt}'| jq '.number')
+
+          for num in $cmd; do
+            gh pr lock --repo "$REPO" --reason "resolved" "$num"
+          done
+        env:
+          GITHUB_TOKEN: ${{ secrets.FLATHUBBOT_TOKEN }}
+          REPO: flathub/flathub