build: extracted UI components to ui-kit in plugin-base-frontend

[berezinant]

Fixes: #3460 #3461 #3462

The UI component is just a couple of js and css files which are conntected to the markup by bem, if possible The assets (ts and scss) are compiled by webpack, the results are stored in plugin-base as plain files js and css (both minified and non-minified for the sake of possible customization by users) files and committed to the repo.