[internal] switch to using workflows to lock old issues

* GitHub's Lock bot has been replaced with a new lock action -> Use this.

.github/workflows/lock.yml

@@ -0,0 +1,19 @@
+# Configuration for https://github.com/dessant/lock-threads
+name: 'Lock Threads'
+
+on:
+  schedule:
+    - cron: '0 0 * * *'
+
+jobs:
+  lock:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: dessant/lock-threads@v2
+        with:
+          github-token: ${{ github.token }}
+          issue-lock-inactive-days: '90'
+          issue-lock-comment: >
+            This thread has been automatically locked since there has not been
+            any recent activity after it was closed. Please open a new issue
+            if you think you have a related problem or query.