Rollup merge of #40988 - eugene-bulkin:ascii-docs, r=frewsxcv
Rollup merge of #40988 - eugene-bulkin:ascii-docs, r=frewsxcv

API Docs: ascii

Add/update docs for the `ascii` module per #29341.

r? @steveklabnik

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