How to add button to top of theme customizer?

Question

I am trying to figure out how exactly I can add a button to the top of the theme customizer. The spot I am talking about is where the "close" and "save" buttons are. The ones that are above everything else and directly above the preview panel.

Would this have to be done through a modification of the core WP files or can it be done through the theme and customizer API itself? If it can be done without modifying the core wordpress files then how can I access it?