Tailwind v4 compatibility

[MichalBryxi]

Since tailwind.config.js is going away in v4, respective part of frontile documentation seems to be obsolete. From my understanding the @source directive is now supposed to be something like:

// app/styles/app.css

// NOTE: this is NOT working for me now, TBD how to make it work
@source '../../node_modules/@frontile/theme/dist';