[ANGULAR] Create a demo showing Angular as event editor

[jsakalos]

Forum post

Notes:

• Angular component (custom element) cannot be used as editor directly
• I plan to extend a field and use Angular component converted to custom element as input field for this extension
• This could probably become a sort of a special Angular wrapper for cell editing – depending on results
• Or it could be used as "Custom" field in vanilla too. Field class currently uses <input> as input element but that could be probably changed easily to use any tag; custom element's tag.