Use `renderToPipeableStream` instead of `renderToString` in `ssr-react` playground

Description

The playground ssr-react uses in the entry-server.jsx the method ReactDOMServer.renderToString which does not support streaming or lazy / suspense components. I'd suggest to replace it with ReactDOMServer.renderToPipeableStream.

Suggested solution

I have made a working example based on the playground (a tiny bit more complex, but in essence the same) here:

https://github.com/technologiestiftung/vite-react-ssg-example/blob/feat/add-streaming-for-suspense/src/entry-server.tsx

If desired, I can make a PR to add these changes. As far as I can tell, nothing else would need to be changed.

Alternative

No response

Additional context

No response

Validations

• Follow our Code of Conduct
• Read the Contributing Guidelines.
• Read the docs.
• Check that there isn't already an issue that request the same feature to avoid creating a duplicate.

Start in playground/ssr-react/entry-server.jsx and inspect how the server-rendered output is produced. Compare it with the linked streaming example, then verify that the playground uses renderToPipeableStream so streaming and lazy or Suspense components are supported.