This is a standalone copy of the code in https://github.com/mdn/yari/ that converts from MDN's Markdown into HTML. That in turn uses mostly packages from unified to convert GFM, with some custom extensions, as documented in https://developer.mozilla.org/en-US/docs/MDN/Writing_guidelines/Howto/Markdown_in_MDN.
The mdn/yari code is used under the MPL 2.0 license.