Add Claro ckeditor5-stylesheets config

Postponed on #3194084: Support functionality equivalent to ckeditor_stylesheets

Problem/Motivation

In #3194084: Support functionality equivalent to ckeditor_stylesheets, a new ckeditor5-stylesheets theme configuration was created. It provides functionality similar to ckeditor_stylesheets, but exists as a separate settings as there are scenarios where a stylesheet that works well in CKEditor 4 won't necessarily work well in CKEditor 5.

Since this theme has ckeditor_stylesheets configured, it should get a ckeditor5-stylesheets setting. It may be possible to use the same stylesheets, but manual testing will be required to confirm the styling is desirable and doesn't have side effects. This is especially necessary as CKEditor5 stylesheets are not encapsulated in an <iframe>

Steps to reproduce

Proposed resolution

Remaining tasks

User interface changes

API changes

Data model changes

Release notes snippet