10403: feat: Add semantic token modifier for crate root r=Veykril a=lhvy
Resolves#9073
I managed to implement crate root highlighting for crates mentioned specifically by name (e.g. `serde` in `use serde::Serialize;`), but not for crates referred to with `crate` or `super`. How could I implement this?
> P.S. I'm participating in [Hacktoberfest 2021](https://hacktoberfest.digitalocean.com/). If this PR is up to standard and merged, I'd appreciate if the `hacktoberfest-accepted` label could be added. Thanks!
Co-authored-by: lhvy <me@lhvy.dev>