ci: Add some more commit message rules

Now that we have the ability to easily define custom rules, add some
more to enforce the existing commit message style.

Part-of: <https://gitlab.gnome.org/GNOME/gnome-shell-extensions/-/merge_requests/149>

.gitlab-ci/commitrules.yml

@@ -2,3 +2,12 @@ patterns:
   deny:
     - regex: '^$CI_MERGE_REQUEST_PROJECT_URL/(-/)?merge_requests/$CI_MERGE_REQUEST_IID$'
       message: Commit message must not contain a link to its own merge request
+    - regex: '^extensions/'
+      message: Commit message subject should not be prefixed with 'extensions/', use the extension name instead
+      where: subject
+    - regex: '^[^:]+: [a-z]'
+      message: "Commit message subject should be properly Capitalized. E.g.  'window: Marginalize extradicity'"
+      where: subject
+    - regex: '^\S*\.js:'
+      message: Commit message subject prefix should not include .js
+      where: subject