Update doc/development/contributing/merge_request_workflow.md

doc/development/contributing/merge_request_workflow.md

@@ -69,7 +69,7 @@ request is as follows:
       the issue(s) once the merge request is merged.
 1. If you're allowed to (Core team members, for example), set a relevant milestone
    and [labels](issue_workflow.md).
-1. If the MR changes the UI, it should include *Before* and *After* screenshots.
+1. If the MR changes the UI, you'll need approval from a Product Designer (UX), based on the appropriate [product category](https://about.gitlab.com/handbook/product/categories/). UI changes should use available components from the GitLab Design System, [Pajamas](https://design.gitlab.com/). The MR must include *Before* and *After* screenshots. 
 1. If the MR changes CSS classes, please include the list of affected pages, which
    can be found by running `grep css-class ./app -R`.
 1. Be prepared to answer questions and incorporate feedback into your MR with new