NewCallBox+CallDisplay: UI facelift

This adds a style.css file to allow the use of custom css

Fixes Librem5/calls#115:
- Making the phone number larger
- Moving the delete button to the bottom
- Rounding all buttons, and making the grid buttons circular
- Making the call button a bit less wide
parent bcaf92d8
Pipeline #51563 passed with stages
in 12 minutes and 49 seconds