[Components] More advanced code block features

[marvin-j97]

Nextra and Vitepress both use Shiki to render code blocks and and thus their feature set seems to be way superior, like:

• Highlighting lines
• Highlighting substrings
• Focused lines
• Git-style diffing
• Line numbers

[atinux]

Docus uses Nuxt Content that also uses Shiki under the hood.

[marvin-j97]

Highlighting lines works, but not correctly in dark mode

[Tahul]

@bdrtsky could you look into this?