Actions: Update PR triggers for submodule pointer check

This ensures the check is run when a draft PR
for bumping the submodule is brought out of draft.

.github/workflows/check-submodule-pointers.yml

@@ -6,6 +6,11 @@ on:
     branches: [ main ]
   pull_request:
     branches: [ main ]
+    types:
+      - opened
+      - synchronize
+      - ready_for_review
+      - reopened
   schedule:
     - cron: '42 12 * * *'