Allow rustup doc books open subsections and paragraphs#3380

YegorStolyarov wants to merge 2 commits intorust-lang:masterrust-lang/rustup:masterfrom

YegorStolyarov:allow_rustup_doc_--book_open_subsections_and_paragraphsYegorStolyarov/rustup:allow_rustup_doc_--book_open_subsections_and_paragraphsCopy head branch name to clipboard