docs: fix preview examples

[danielleroux]

🆕 What is the new behavior?

• Change react-test-app jsx transformer to react-jsx transformer
• Downgrade docusaurus because up from 3.4 docusaurus postprocess static-folder css files (Docusaurus 3.4.0+ does not respect PostCSS plugins when it minimizes CSS files from 'static' folder facebook/docusaurus#10334)

🏁 Checklist

A pull request can only be merged if all of these conditions are met (where applicable):

• 🦮 Accessibility (a11y) features were implemented
• 🗺️ Internationalization (i18n) - no hard coded strings
• 📲 Responsiveness - components handle viewport changes and content overflow gracefully
• 📄 Documentation was reviewed/updated (pnpm run docs)
• 🧪 Unit tests were added/updated and pass (pnpm test)
• 📸 Visual regression tests were added/updated and pass (Guide)
• 🧐 Static code analysis passes (pnpm lint)
• 🏗️ Successful compilation (pnpm build, changes pushed)

👨‍💻 Help & support

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Latest commit: 0e1d1a5

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[github-actions]

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