Enable all main body Markdown options for summaries
Enable all main body Markdown options for summaries

This fixes odd renderings when these features are used in the first
paragraph of documentation for an item. This is an extension of #87270.

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