Document use cases where XB's field widgets don't 1:1 match how they would work in a twig theme

Note: include a mention of function xb_stark_preprocess_field_multiple_value_form which should be there after 📌 Add e2e tests for multi-value textfield widget in page data form Active as that is some extra lifting that wouldn't be needed without Radix & the templates were more analagous to our Twig ones.

Let's document this while it's still fresh in your head 😊

📌 Support props that can use wysiwyg widgets Active is in!

Feedback addressed

just fixed some missing punctuations and cspell. merged thanks!