Rollup merge of #34667 - KaivoAnastetiks:fix/crate-documentation, r=Manishearth
Rollup merge of #34667 - KaivoAnastetiks:fix/crate-documentation, r=Manishearth

Add a section about crate documentation.

Fixes #34329
?r @steveklabnik

GBGamer/rust,GBGamer/rust,aidancully/rust,graydon/rust,graydon/rust,graydon/rust,aidancully/rust,GBGamer/rust,GBGamer/rust,graydon/rust,graydon/rust,graydon/rust,GBGamer/rust,aidancully/rust,GBGamer/rust,aidancully/rust,aidancully/rust,GBGamer/rust,aidancully/rust,GBGamer/rust