If CKEditor gets a "Stark" skin, we should document how to leverage that

Ideally CKEditor would have a "skin" (CKEditor lingo for "theme" in the Drupal world) similar to Drupal's Stark theme, which would make it easier to customize the look and feel of CKEditor.

This requires no work on the Drupal side besides adding documentation. This issue is effectively blocked on this CKEditor ticket: https://dev.ckeditor.com/ticket/10964.