docs: add `next.config.ts` Node.js native resolver (#83561)
This PR adds docs for using Node.js native TS resolver for
`next.config.ts`. It states:
- Supports Node.js native TS resolver
- Why use it
- How to use it
- Restrictions
- Why use `next.config.mts`
I didn't mention how much it's faster compared to the legacy resolver
(~68% faster in the hello world app -
[link](https://github.com/vercel/next.js/pull/83240)) because the
experience may vary for users.
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Co-authored-by: Joseph <joseph.chamochumbi@vercel.com>
Co-authored-by: Abdón Rodríguez <a@abdonrd.com>
