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 {
   		[ UploadAdapter.pluginName ]: UploadAdapter;
   	}
   }

• Update index.ts to import the augmentation file.

   import './augmentation';

• Update tsconfig to include DOM.Iterable
  

  ckeditor5-package-generator/packages/ckeditor5-package-generator/lib/templates/ts/tsconfig.json.txt

  Lines 3 to 5 in 64bdb5e

  	"lib": [
  	"DOM"
  	],

• 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: ckeditor/ckeditor5#13929

[martnpaneq]

Sure, PR for docs is here: ckeditor/ckeditor5#13935.