4394: Simplify r=matklad a=Veetaha
4414: Highlighting improvements r=matklad a=matthewjasper
- `static mut`s are highlighted as `mutable`.
- The name of the macro declared by `macro_rules!` is now highlighted.
Co-authored-by: veetaha <veetaha2@gmail.com>
Co-authored-by: Matthew Jasper <mjjasper1@gmail.com>