Use prism.js as code highlighter

[HerrBertling]

The code highlighting is a bit plain right now. I want to change this.

I liked prism.js in the design system I helped build at Xing. It looks quite nice, is easy to integrate (=> https://www.yasminzy.com/tutorial/prism.html#installation ) and if we're very bored, we could even build an own theme for it. Which isn't even that hard to accomplish :)

Would look similar to this:

[lassediercks]

Can only recommend prism, works like a charm