Add workflow for locking old issues (#3980)

To avoid necroposting to old issues that's usually left unnoticed, add workflow
for locking issues similar to the one that Core has.

The PR locking limit can be increased as the traffic is much lower compared to
Core. Issues before 2025 have been locked manually via the API.

.github/workflows/lock.yml

@@ -0,0 +1,20 @@
+name: Lock
+
+on:
+  schedule:
+    - cron: "0 * * * *"
+
+jobs:
+  lock:
+    if: github.repository_owner == 'home-assistant'
+    runs-on: ubuntu-latest
+    steps:
+      - uses: dessant/lock-threads@v5.0.1
+        with:
+          github-token: ${{ github.token }}
+          issue-inactive-days: "30"
+          exclude-issue-created-before: "2025-01-01T00:00:00Z"
+          issue-lock-reason: ""
+          pr-inactive-days: "7"
+          exclude-pr-created-before: "2025-01-01T00:00:00Z"
+          pr-lock-reason: ""