https://github.com/css-modules/css-modules
https://github.com/css-modules/icss

https://github.com/webpack-contrib/css-loader
Webpack's css-loader in module mode replaces every local-scoped identifier with a global unique name (hashed from module name and local identifier by default) and exports the used identifier.
Extending adds the source class name(s) to the exports.
Extending from other modules first imports the other module and then adds the class name(s) to the exports.