[syntax-highlighting] use shiki

[vassbence]

shiki has a simple and straightforward integration with monaco for syntax highlighting: https://shiki.style/packages/monaco.

It could replace the current hand-rolled solution. Let me know if you'd be interested in this, if yes I'll be more than happy to implement it.

[milomg]

That seems great! Hopefully if we use Shiki's oniguruma-to-es compiler instead of onigasm we can also shrink the bundle size