chore(repo): Add merge_group trigger to checks.yml (#1907)

As described in https://docs.github.com/en/repositories/configuring-branches-and-merges-in-your-repository/configuring-pull-request-merges/managing-a-merge-queue

.github/workflows/checks.yml

@@ -1,5 +1,6 @@
 name: Quality checks and tests
 on:
+  merge_group:
   pull_request:
     branches: [ main ]