Scoped themes to apply only to the editor (#editor-holder)

https://github.com/adobe/brackets/issues/8415
https://github.com/adobe/brackets/issues/8420
Yeah they do. It's a simple change. It's just basically what we had talked about. Converting the theme string into an object with a file field... I am storing off the dark flag but it's not being added to the dom quite yet. I can adjust the default themes if you'd prefer... Or if you already there go ahead and dot it :)