Improved CSS Syntax Highlighting

[treykane]

First off... Thank you, for bringing a new version of this theme into the Zed editor!

I'm noticing a lot of my CSS particularly when nested is not getting the syntax highlighting I would expect.

I may be able to contribute and help with updating this, but I wanted to create the issue for the moment, in case this was already being addressed.

Thank you again, I'll follow up if I start working on this issue!