Add Rust language support

### Is your feature request related to a problem? Please describe
N/A

### Describe the solution you'd like

It would be really nice if you could add syntax highlighting support for the Rust language. Thanks! :)

### Describe alternatives you've considered
N/A

### Additional context
N/A

Start by reading the repository's existing language-support implementation and any tests or registration entry points for syntax brushes. Add Rust syntax highlighting following those conventions, then run the relevant test suite and verify that Rust snippets are highlighted correctly.

Written by the indexing model from the issue text.