Support for JSX automatic runtime

Start by tracing React-Live's Sucrase transformation path, focusing on how JSX is currently compiled and where transform options are exposed. Add support for selecting React's automatic JSX runtime, then verify that React 19 no longer reports the outdated JSX transform warning in live playgrounds.

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Feature Request

When upgrading Docusaurus to React 19, I noticed some warnings in documentation pages containing React-Live playgrounds

It turns out React 19 has a new warning in dev mode:


VM59912:5 Your app (or one of its dependencies) is using an outdated JSX transform. Update to the modern JSX transform for faster performance: https://react.dev/link/new-jsx-transform Error Component Stack
    at Hello (<anonymous>)
    at ErrorBoundary (eval at ../node_modules/react-live/dist/index.mjs (vendors-node_modules_parse-numeric-range_index_js-node_modules_react-live_dist_index_mjs-node-bdedd5.js:338:1), <anonymous>:161:10)
    at div (<anonymous>)
    at LivePreview (eval at ../node_modules/react-live/dist/index.mjs (vendors-node_modules_parse-numeric-range_index_js-node_modules_react-live_dist_index_mjs-node-bdedd5.js:338:1), <anonymous>:331:29)
    at ErrorBoundary (eval at ../packages/docusaurus/lib/client/exports/ErrorBoundary.js (main.js:1021:1), <anonymous>:29:9)
    at BrowserOnly (eval at ../packages/docusaurus/lib/client/exports/BrowserOnly.js (__comp---theme-blog-post-pageccc-cab.js:488:1), <anonymous>:19:24)
    at Preview (<anonymous>)

By default, React-Live is using Sucrase to transform the code, but there's no ability to customize the JSX runtime (classic by default).

An option to turn on the automatic runtime would be welcome to get rid of this warning.

To be honest, I'm not 100% sure why there is a warning, considering React.createElement is considered fine although not optimal according to the linked page.

Note
The functions inside react/jsx-runtime and react/jsx-dev-runtime must only be used by the compiler transform. If you need to manually create elements in your code, you should keep using React.createElement. It will continue to work and is not going away.

In any case, it looks future proof to support the automatic runtime in this lib