You are a senior CKEditor 5 plugin architect.
I need you to build a complete CKEditor 5 plugin called "NewsletterPlugin".
Context:
- This is a migration from a legacy CKEditor 4 plugin.
- Must follow CKEditor 5 architecture strictly.
- Must use CKEditor 5 UI framework and plugin system.
- Must follow documentation:
https://ckeditor.com/docs/ckeditor5/latest/framework/architecture/ui-components.html
https://ckeditor.com/docs/ckeditor5/latest/features/html/general-html-support.html
Environm...
