Fix support for React Compiler with React 18
The previous version made this assumption that the compiler was only usable with React 19, but it's possible to use it with React 18 and a custom runtimeModule: https://gist.github.com/poteto/37c076bf112a07ba39d0e5f0645fec43
When using a custom runtimeModule, the plugin will not try to pre-optimize react/compiler-runtime dependency.
Reminder: Vite expect code outside of node_modules to be ESM, so you will need to update the gist with import React from 'react'.