Document how the `RwLockReadGuard` structure is created.
Document how the `RwLockReadGuard` structure is created.

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