There should be configurable ignore css glob

[candunaj]

There is a hardcoded extension to ignore in scoped-css-preprocessor.js.

It should be configurable in a config.

Background

As we wanted to support ember-scoped-css side by side with ember-css-modules we moved all css files to *.module.css. And setup an extension for ember-css-modules to module.css. This extension needs to be ignored otherwise the scoped-css-preprocessor will check if co-located components exist for those files and that can be time-consuming.