Support separation of Rust namespaces/modules and generic angle brackets for theming

[Mettwasser]

Been trying Zed for the past couple of days and been having a blast, alltho there is one major thing that nags me:

Visual seperation of rust modules. As far as I know there's no way to make them visually distinct from variables.

Another thing, as the title suggests, are generic angle brackets/turbofish operators. They just fall under "operator", which, for me at least, makes it somewhat hard to distinguish them at first glance, alltho that's not a big deal.

Would be very nice if you could give namespaces a distinct color.