Add React 18 support

[fkapsahili]

This is a proposal to add support for React 18. For React 18, ReactDOM.render and ReactDOM.hydrate are deprecated, so the new ReactDOM.createRoot and ReactDOM.hydrateRoot methods must be used:

https://react.dev/reference/react-dom/client/createRoot#createroot https://react.dev/reference/react-dom/client/hydrateRoot#hydrateroot

Since the SSR examples are quite old and Hypernova has also been deprecated, I have not yet been able to extensively test the case where hydrateRoot is used. Unfortunately, I can no longer get the old SSR examples to work because the node version is too old 🙂. Can you check if it works or let me know how I can test it?