Allow sass files to be create different css files.

Problem/Motivation

SCSS that can be compiled into different CSS files to be used on different themes are needed for example the default and admin theme.

1. Make an upstream request to the Reactjs editor developer to develop an input for a separate CSS file to be created.
2. Upsteam a request to the developers to add a checkbox so CSS can be added to the header inline.
3. Allow the module to apply different styles to different themes.