Support React 19 in the React SDK

[ikovic]

Description

Ensure that all the imports from react and react-dom are externalized. The problem was that rollup only externalizes the deps only if their imports match the expression exactly, so react/jsx-runtime and react-dom/client were included in the bundle.

Checklist

• I have added tests that prove my fix is effective or that my feature works
• I have generated the new version of the docs website and smoke tested it
• I have checked that my changes haven't caused semantic errors in the existing docs
• I have generated a changeset if my change affects the published packages

[cloudflare-workers-and-pages]

Deploying website-react-storybook with    Cloudflare Pages

Latest commit:	88d798f
Status:	✅  Deploy successful!
Preview URL:	https://a43ddf61.website-react-storybook.pages.dev
Branch Preview URL:	https://sid-update-react-19.website-react-storybook.pages.dev

View logs

[github-actions]

Bundle size comparison

Name	+/-	Base	Current	+/- gzip	Base gzip	Current gzip
main.js	+55.76%	414.02 kB	644.88 kB	+41.15%	108.82 kB	153.60 kB
style.css	=	38.27 kB	38.27 kB	=	6.50 kB	6.50 kB
main.d.ts	=	5.63 kB	5.63 kB	=	1.39 kB	1.39 kB

Generated by 🚫 dangerJS against 88d798f