Function to_markdown_with_code 

pub fn to_markdown_with_code(blocks: &[Block], code: bool) -> String

to_markdown, with the monospace runs as code or as plain text (#636).

Preview: output quality is still improving and the API may change in a minor release.

False writes what to_markdown wrote before code existed: the runs are still found, they are just not marked. The switch ExtractOptions::code reads.