Webpack 5 support (module federation)

Created by: bradydowling

Is your proposal related to a problem?

It would be great to be able to use federated modules in Webpack with a CRA application.

Describe the solution you'd like

Provide support for Webpack 5 by upgrading the default Webpack version to 5. This was previously requested (https://github.com/facebook/create-react-app/issues/6081) but closed because Webpack 5 wasn't in beta at the time. It is now in beta and has had several releases.

Describe alternatives you've considered

You could also allow an opt-in to using Webpack 5 (just like Next.js does) when users initially run CRA from the command-line.