Rollup merge of #36841 - GuillaumeGomez:process_doc, r=steveklabnik
Rollup merge of #36841 - GuillaumeGomez:process_doc, r=steveklabnik

Improve process module doc a bit

r? @steveklabnik

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