webpack-5 and webpack-4 compatibility issue

This is an example library built with webpack 5 to demo an issue when consumed in an app that uses webpack 4.

1. In module directory is a js module that is bundled with webpack 5.
2. In library directory is a js library that is bundled with webpack 5 and re-exports the webpack-5 bundled module, leaving it as external.
3. In app directory is a js app that is bundled with webpack 4 that tries to use module through library.

Repro steps:

1. cd app;
2. npm ci;
3. npm start;
4. Open http://localhost:8080/, see error in console: Uncaught TypeError: i[e] is not a function

Conditions necessary to reproduce the issue:

• module and library are bundled with webpack@5
• library is bundled with TerserPlugin with keep_fnames: true
• library has a async loaded module
• app is bundled with webpack@4