add message styling

[mattmezza]

Would be nice to have the ability to send message with a lil bit of formatting like:

• bold *bold*
• italic /italic/
• underline _underline_
• line through ~line through~
• code inline `var pippo = 0;`

[coyotte508]

This repo is useful: https://www.npmjs.com/package/marked

Although it adds an extra dependency (20kB), which could also be moved the backend instead.

[mattmezza]

@coyotte508 indeed, and also I think it is too much for what we would use it for...
I was thinking to use something lighter or to create a light package for it (eventually, it should not be that difficult).

We don't wanna add full support to markdown, but just a small set of formatting options (I'm not even sure about the underline for instance...).

[mattmezza]

It is also related to #24 (you might wanna go back to a previous msg to strike through something for instance)

[mattmezza]

working on this, almost ready ;)

[mattmezza]

added using https://github.com/mattmezza/msgdown