Created by: emiliogarza
I had a need for a Background Color utility class for a gray color. So I noticed that the $theme-colors map was being looped into the bg-variant mixin and but not the $grays map. I think it could be useful to others to have the bg-variant mixin classes created for the $grays like the $theme-colors to give more utilities for the all colors they define in variables.
This is my first Pull Request so please let me know if I need to do anything differently and your thoughts!