feat: support webpack 5

[ruscon]

As I see, you have a lot of real dependencies here
https://github.com/saltyshiomix/react-ssr/blob/master/packages/core/package.json

Apparently, this is the cause of problems for some webpack plugins, because multiple versions of webpack are installed at the same time (webpack@5 by project and webpack@4 by your library)

I think many dependencies can (and should) be moved to peerDependencies