Rollup merge of #62462 - JohnTitor:document-while, r=Centril
Rollup merge of #62462 - JohnTitor:document-while, r=Centril

Document `while` keyword

This is a rework of #60761.
Closes #60736

r? @dtolnay

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