Make ra work with doc comments

[TadoTheMiner]

Rustfmt already does, don't see a reason why it shouldn't

[lnicola]

Can you say more exactly what you mean?

[TadoTheMiner]

Rust analyzer doesn't work in code snippets inside doc comments.

[ChayimFriedman2]

Semantic highlighting does work for code inside doc comments. But yeah, most IDE features don't, and it's hard to make them work.