☂️ CSS support

Description

We are going to use this issue to track the various work around CSS. We don't plan, for the time being, to support super languages, although we might think about preparing the infrastructure to be able to support them.

PREVIOUS DISCUSSIONS: https://github.com/rome/tools/issues/984

• create a css.ungram file where we will slowly implement new grammars
• create a rome_css_syntax crate, where we will have all things related to the CSS syntax, generated code too
• expand the codegen of the grammar to include CSS too
• evaluate how to implement the parser, lexer, etc. (it will require a separate discussion)
• create a rome_css_formatter crate
• make the rome_formatter generic
• prepare the Rome architecture to include CSS (file handlers, capabilities, etc.)
• add support for CSS inside the VSCode extension