Steps to reproduce

1. Configure a rich text field with fontSizes: tiny;small;big;huge (i.e. on mtk2/dialogs/components/textImage.yaml)
2. Create a page with Text and Image component
3. Click on Font Size button on the rich text field

Expected results

Tiny, Small, Big, Huge options should be present on the option field

Actual results

9, 11, 13, Default, 17, 19, 21 options are present on the option field, see attached picture

Development notes

CKEditor5Config class declares fontSizes field but ckeditor5 expects fontSize