Update styles to match latest highlight.js release

[SystemKeeper]

Hello, thank you for this library - very cool!

I am wondering if it would be (easily?) possible to update the styles to the latest versions found in highlight.js. Especially github and the now added github-dark seem to be quite different nowadays. I manually tried to download and minimize the files, but it seems I am missing some step in between to make it work correctly (or maybe the library changed in the meantime, I didn't dive into this in too much detail).