Issue #3274937 by nod_, woldtwerk, Dom., Wim Leers: Get CKEditor 5 to work in (modal) dialogs

core/modules/ckeditor5/ckeditor5.module

core/modules/ckeditor5/css/ckeditor5.dialog.fix.css

core/modules/ckeditor5/js/ckeditor5.dialog.fix.es6.js

core/modules/ckeditor5/js/ckeditor5.dialog.fix.js

...5/tests/modules/ckeditor5_test/ckeditor5_test.routing.yml

...or5_test/src/Controller/CKEditor5DialogTestController.php

...r5/tests/src/FunctionalJavascript/CKEditor5DialogTest.php