Add missing exports

[FilipTokarski]

📝 Provide detailed reproduction steps (if any)

Request to export the following from ckeditor5 package:

• import type { ColorSelectorDropdownView } from '@ckeditor/ckeditor5-font/src/utils';
• import DocumentColorCollection from '@ckeditor/ckeditor5-ui/src/colorselector/documentcolorcollection';
• import { SchemaCompiledItemDefinition } from '@ckeditor/ckeditor5-engine/src/model/schema';
• import ClassicEditorUIView from '@ckeditor/ckeditor5-editor-classic/src/classiceditoruiview';
• import { DowncastAttributeEvent } from '@ckeditor/ckeditor5-engine/src/conversion/downcastdispatcher';
• import { add } from '@ckeditor/ckeditor5-utils/src/translation-service';

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