Rust: make references be distinguishable

[zanedp]

Ideally, the color theme should make things that aren't obvious from the local syntax stand out. When editing Rust code, it's not clear from syntax when a variable is a reference, especially when using type interference or chained iterators.

I suggest that rather than have property accesses be in italic, have references be in italic.

I have no trouble telling syntax when I'm accessing a property (there's a dot!), but I don't always know if something is a reference until the compiler yells because I didn't use a reference like a reference (or vice versa).

I have found adding these to my editor.sematicTokenColorCustomizations in settings helps me out a ton when editing Rust code because it makes it obvious whether something is a reference or not: variables that are references are italics, and methods that take a reference to self (&self or &mut self) are also italicized.

"enabled": true,
"property": {
    "italic": false,
},
"*.reference": {
    "italic": true
},
"*.mutable": {
    "bold": true
},
"*.consuming": {
    "underline": true,
},

This request is probably related to #43.

Edit 2024-08-31: Updated to use italic property rather than fontStyle. Also added mutable and consuming which are helpful distinguishers when editing Rust code.