Visual Builder Application Extension change styles

Summary:

I want to modify the default css or link a new one to override the default.

Content (required):

Hello,

I'm making some developments usign the new option to make Application Extensions for Fusion Apps. The default styles that the page is using does not match very well and the menus that we are able to create are very different from the standard screen icons.

Is there a way to modify the stylesheet or link a new one to get something closer to the standard menus?