Important: #107063 - CKEditor 5 v46.1.0: TypeScript imports and CSS changes 

Description 

With the upgrade to CKEditor 5 v46.1.0, three relevant changes are made:

1. The API naming of TypeScript type imports has changed a lot. Any custom CKEditor 5 plugin using TypeScript type imports in their build chain will need to be adapted to match these imports. See https://ckeditor.com/docs/ckeditor5/latest/updating/nim-migration/migrating-imports.html for a large table of "before->after" renames. This is not considered a breaking change in context of TYPO3 integration, because existing JavaScript modules will continue to work, as TypeScript type imports are not part of the final output. Runtime imports that are exposed by the @ckeditor5/ckeditor-* modules have not been changed and will continue to work.
2. A new opinionated default CSS is used by CKEditor to apply some improved styling over contents displayed within the RTE interface. Most of these are overruled by TYPO3's default CSS integration though. Possible customizations need to respect this.

3. A few CSS classes have been renamed, see https://ckeditor.com/docs/ckeditor5/latest/updating/guides/update-to-46.html. These are for example referenced in custom CKEditor YAML configurations like the following diff, and need to replace the color subkey:

   Configuration/RTE/Full.yaml - Before/After

    - {
        model: 'yellowMarker',
        class: 'marker-yellow',
        title: 'Yellow marker',
        type: 'marker',
   -    color: 'var(--ck-highlight-marker-yellow)'
   +    color: 'var(--ck-content--highlight-marker-yellow)'
      }
    - {
        model: 'greenMarker',
        class: 'marker-green',
        title: 'Green marker',
        type: 'marker',
   -    color: 'var(--ck-highlight-marker-green)'
   +    color: 'var(--ck-content-highlight-marker-green)'
      }
    - {
        model: 'redPen',
        class: 'pen-red',
        title: 'Red pen',
        type: 'pen',
   -    color: 'var(--ck-highlight-pen-red)'
   +    color: 'var(--ck-content-highlight-pen-red)'
      }

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Affected installations 

TYPO3 installation relying on custom or third-party CKEditor 5 TypeScript build chains, or CSS adaptations that no longer match the CKEditor 5 naming.

Possible Migration 

Follow the CKEditor 5 upgrade guide to change CSS class names and TypeScript imports.