enhancement/issue 1320 upgrade markdown related dependencies to latest

[thescientist13]

Related Issue

resolves #1320

Documentation

1. Document removal of settings option from markdown configuration

Summary of Changes

1. Upgrade all markdown related dependencies
2. Remove support for markdown settings configuration (since remark-parse no longer takes any options - https://www.npmjs.com/package/remark-parse#api)

GFM

Can confirm this is all working now and outputting the expected HTML
https://www.npmjs.com/package/remark-gfm/v/1.0.0#use

Definitions List

The reported issue with <dl> rendering seems more to do with just general formatting around markdown in general. For example, looking at the file in an IDE with and without indentation, we can see syntax highlight lighting up in the formatted version

For example, markdown formatting inside HTML blocks will just get processed as HTML per the spec, so pretty much I think this is all working as expected.

An HTML block is a group of lines that is treated as raw HTML (and will not be escaped in HTML output).

TODO

1. validate definitions list
2. see if any of this helps with - hyphens and quotes in markdown code fence results in missing content with production builds #1325 - no luck unfortunately
3. remove demo code