TypeScript version of the generated plugin should reflect CKEditor 5 features

[pomek]

Provide a description of the task

During the last TS sync, we agreed that packages produced by the tool should be in-line with official CKEditor 5 packages.

It means we should:

• Create the augmentation.ts file. Example content below:

  import type { UploadAdapter } from './index';
  
  declare module '@ckeditor/ckeditor5-core' {
      interface PluginsMap {
      }
  }

• Update index.ts to import the augmentation file.

  import './augmentation';

• Update tsconfig to include DOM.Iterable https://github.com/ckeditor/ckeditor5-package-generator/blob/64bdb5ee66fff628a2fd2abc8a4e435f5e5bbece/packages/ckeditor5-package-generator/lib/templates/ts/tsconfig.json.txt#L3-L5
• Update generated sample/index.html to reflect recent changes.

[pomek]

Let's mention what the augmentation.ts file should contain:

• https://ckeditor.com/docs/ckeditor5/latest/api/module_core_plugincollection-PluginsMap.html
• https://ckeditor.com/docs/ckeditor5/latest/api/module_core_commandcollection-CommandsMap.html

[Witoso]

Could we tweak the docs as well? Rel: https://github.com/ckeditor/ckeditor5/issues/13929

[martnpaneq]

Sure, PR for docs is here: https://github.com/ckeditor/ckeditor5/pull/13935.