Messages should support simple markdown

[haadcode]

It should be possible to add markdown to messages.

There isn't a implementation for proper multi-line messages atm. so this could be a limited markdown, a subset.

I'm thinking the following should be included:

• Italics
• Bold
• Code block
• ~~Strikethrough~~

The markdown should be parsed from the message before rendering. This can be done similar to emojify and linkify parts of the message rendering.

[dignifiedquire]

Inline code would also be super nice like this