15 files declare their use of CKEditor5 in Drupal 10

ckeditor5.module in core/modules/ckeditor5/ckeditor5.module

CKEditor5CKEditor4Compatibility.php in core/modules/ckeditor5/tests/src/FunctionalJavascript/CKEditor5CKEditor4Compatibility.php

CKEditor5DialogTest.php in core/modules/ckeditor5/tests/src/FunctionalJavascript/CKEditor5DialogTest.php

CKEditor5IntegrationTest.php in core/modules/quickedit/tests/src/FunctionalJavascript/CKEditor5IntegrationTest.php

CKEditor5Test.php in core/modules/ckeditor5/tests/src/FunctionalJavascript/CKEditor5Test.php

CKEditor5Test.php in core/modules/ckeditor5/tests/src/Unit/CKEditor5Test.php

CKEditor5ValidationTestTrait.php in core/modules/ckeditor5/tests/src/Kernel/CKEditor5ValidationTestTrait.php

EmphasisTest.php in core/modules/ckeditor5/tests/src/FunctionalJavascript/EmphasisTest.php

ImageTest.php in core/modules/ckeditor5/tests/src/FunctionalJavascript/ImageTest.php

MediaLibraryTest.php in core/modules/ckeditor5/tests/src/FunctionalJavascript/MediaLibraryTest.php

MediaTest.php in core/modules/ckeditor5/tests/src/FunctionalJavascript/MediaTest.php

SourceEditingTest.php in core/modules/ckeditor5/tests/src/FunctionalJavascript/SourceEditingTest.php

StyleTest.php in core/modules/ckeditor5/tests/src/FunctionalJavascript/StyleTest.php

TableTest.php in core/modules/ckeditor5/tests/src/FunctionalJavascript/TableTest.php

WildcardHtmlSupportTest.php in core/modules/ckeditor5/tests/src/Kernel/WildcardHtmlSupportTest.php