docs: add third parties + scripts documentation

[danielroe]

🔗 Linked issue

📚 Description

🚧 This is a WIP pull request to add documentation for coming nuxt third-parties/scripts implementations.

It's very much subject to change, so don't rely too much on this for now. 😉

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[harlan-zw]

This needs a bit of refactoring:

• we don't expose useStyles anymore
• inline asset strategy is not supported
• the composable names convention is to be prefixed with useScript which is already updated upstream

We need quite a bit of documentation and I don't think the Nuxt core repo is the place for it, so I'm making a dedicated docs site. I intend to pick any usable content from this draft into that.

So not sure what you want to do with this PR

[danielroe]

For now, I think we need authoritative source of docs in standalone nuxt/scripts docs website. Ultimately we might reconsider merging them back into nuxt.com when API surface is stable and docs changes are few or nuxt/scripts is automatically installed as a dependency of Nuxt.

But until then, we should document key utilities like useScript and any other composables that will trigger auto-install of nuxt/scripts with minimal docs pointing to the separate scripts docs website (like we do with nuxt/image).

Feel free to directly push to this branch 🙏