color doc comments differently than normal comments

[andrewrk]

// normal comment
fn foo() void {}

/// doc comment
fn foo() void {}

It helps to show that they will be parsed differently.

[emekoi]

i think i'm going to rework a lot of the syntax file to adhere to this hopefully this doesn't break anything such as the linguist syntax highlighting.

[emekoi]

i think this would require an upstream change on github's part to differentiate between comment.*.documentation scopes and comment.* scopes.

[daurnimator]

Also container-doc-comments (https://github.com/ziglang/zig/pull/3697)