Extended Block style features

[andreilupu]

I love the way Gutenberg allows you to make custom stylisation to headings and paragraphs.

We could take it further and do this with the contact form blocks

[ineagu]

@andreilupu, as we have talked here the most effective approach in this particular case, is to add skins, from the development perspective, a new skin will load a new bunch of CSS rules for the form, while on the right side we'll show a drop-down/radio with 2 styles for start: Default / Material.

I will define a bit more the preview part in a new issue.