CKEditor: Adding source editing button

[SugarShaker]

How do I add the source edit button on the ckeditor navbar.
In ckeditor documentation its:

import { SourceEditing } from '@ckeditor/ckeditor5-source-editing';

ClassicEditor
    .create( document.querySelector( '#editor' ), {
        plugins: [ SourceEditing, /* ... */ ],
        toolbar: [ 'sourceEditing', /* ... */ ]
    } )
    .then( /* ... */ )
    .catch( /* ... */ );

Is there a way to do this in backpack?
I also need to allow div and class tags, once I can edit the source.

Thanks,

Rob

[karandatwani92]

To add more plugins to CKEditor follow the guide here

[SugarShaker]

Great... many thanks.
Do you know of any guides on how to allow different tags and attributes on tags, so ckeditor doesn't strip them out?