Use shiki for code highlight

### Have you read the Contributing Guidelines on issues?

- [X] I have read the [Contributing Guidelines on issues](https://github.com/facebook/docusaurus/blob/main/CONTRIBUTING.md#issues).

### Motivation

Have you guys ever considered switching to Shiki for code highlight, instead of Prism?

I find Shiki a lot nicer, with much better grammars that are able to highlight much more code than Prism does.

Also, [Shiki](https://github.com/shikijs/shiki) is being actively maintained, while [Prism](https://github.com/PrismJS/prism) seems a little bit abandoned. However, even if Shiki wasn't being maintained, its themes would never stop improving since they are taken from VS Code anyway.

Here is a quick comparison I did:

Prism (dracula - the default theme from Docusaurus):


Shiki (dracula):


PS: I'm aware of [docusaurus-preset-shiki-twoslash](https://www.npmjs.com/package/docusaurus-preset-shiki-twoslash), and that's what I used for the example above (https://github.com/felipecrs/shiki-docusaurus-test). This is to suggest a better default for the project as a whole.

Maybe it's a good breaking change candidate for Docusaurus v3?

### Self-service

- [ ] I'd be willing to do some initial work on this proposal myself.