Investigate using the marked vs. markdown-it parser for better Github markdown support

[bfitzpat]

While looking into https://github.com/redhat-developer/vscode-didact/issues/150, it became apparent that while markdown-it supports the CommonMark spec for markdown, it doesn't quite support some of the nice Github-related markdown conventions.

It appears that the https://www.npmjs.com/package/marked component may do the trick, but may require some additional massage of the generated HTML.

See https://marked.js.org/#/USING_PRO.md#renderer as an example