docs: add guide for customizing JSX in React

[chenjiahan]

Summary

This pull request enhances the documentation for customizing JSX guides. It provides detailed instructions on configuring the JSX runtime using @rsbuild/plugin-react and includes examples for both automatic and classic runtimes.

Related Links

• [Feature]: Will jsxCustomEvent be discarded if it is not referenced after import? #4654

Checklist

• Tests updated (or not required).
• Documentation updated (or not required).

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