Support Plain CSS

[regalius]

Is your feature request related to a problem? Please describe.
Sometimes we need to import plain CSS without CSS module, for example when using Material UI

Describe the solution you'd like
I like how Create React App implements CSS & CSS module, They use .css for plain CSS and .module.css for CSS module. To do this we need to change the loader for .css and add .module.css into separate loader entry in our webpack configuration.

Additional context
I believe this would be a breaking change