Expose Webpack bundle5 for development of external packages

[eric-burel]

Describe the feature you'd like to request

I need to use Next.js webpack 5 bundled version in a non-Next application (Storybook).

I need this to allow further development of @next/plugin-storybook, within the following demo application that relies on it: https://github.com/lbke/next-plugin-storybook-demo.
I experience conflicts, because Storybook will install its own version but Next and thus @next/plugin-storybook will rely on their own homemade bundle.

Describe the solution you'd like

Expose Webpack 5 bundle5.js file in Next, for instance as a package, so that it can be used instead of Webpack in end-user application.
Also, I am not sure how I could alias this package, so that webpack is replaced by next/webpack basically (since it's webpack itself, I am not sure I can use a Webpack alias as usual).

Describe alternatives you've considered

Using Yalc to avoid any issue with linking, then copy pasting bundle5.js into node_modules/webpack/lib/index.js, the hard way.
It leads to _webpack.DefinePlugin is not a constructor.

Another alternative would be to remove the explicit dependency to webpack in @next/plugin-storybook.

Reproductions

• Simpler reproduction: Feature/next plugin storybook lbke/next.js#1, check with-storybook-experimental, try to install and run yarn run storybook
• Reproduction and documentation here (using a 2nd app) + a version with webpack 4 that does work: https://github.com/lbke/next-plugin-storybook-demo

[eric-burel]

I've also tried to do the same directly in a fork of Next, same result because Storybook will still load it's own webpack: lbke#1