Support for Front Matter with Markdown page metadata

[gwpl]

Context

Many markdown files I have in repositories contain YAML Front Matter (

• https://jekyllrb.com/docs/front-matter/
• https://gohugo.io/content-management/front-matter/
  ...
  )

Currently mdformat just formats all of this into one line.

Proposal

Can mdformat identify (or have flag) to identify and ignore YAML front matter.

(As ambitious goal, pass it through some YAML formatter if available, but just leaving it as it is would be already huge improvement)

Tasks and updates

No response

[hukkin]

Closing as dupe of #372.

See https://github.com/butler54/mdformat-frontmatter for frontmatter support today.

This may happen in #332