feat: some syntax highlighting improvements

[asterite]

Description

Problem

Resolves #89
Resolves #90

Summary

A few things here.

crate is now highlighted

Before:

After:

Struct members visibility is now highlighted

Before:

After:

Calls with turbofish are colored the same way as calls

Before:

After:

Comments inside use are highlighted

Before:

After:

Additional Context

PR Checklist

• I have tested the changes locally.
• I have formatted the changes with Prettier and/or cargo fmt on default settings.

[TomAFrench]

LGTM