Add markdown support

[pmuens]

This is a good implementation: https://github.com/jimpick/lambda-comments/blob/master/packages/frontend/src/ui/comment.js

[xndrdev]

What about: https://github.com/rexxars/react-markdown ? @pmuens

[pmuens]

I would like to go with those MarkdownIt and highlight.js. They play nicely together:

Here you can see their usage:
https://github.com/jimpick/lambda-comments/blob/master/packages/frontend/src/ui/comment.js#L4
https://github.com/jimpick/lambda-comments/blob/master/packages/frontend/src/ui/comment.js#L16-L32
https://github.com/jimpick/lambda-comments/blob/master/packages/frontend/src/ui/comment.js#L43

[xndrdev]

Ok! I take a look on it and send you a PR.

[pmuens]

Great! Thank you! I'll assign you.