Customize height of button

**Is your feature request related to a problem you're having? Please describe.**
The buttonHeight property is inaccessible and would like the dimensions of the button exposed.

**Describe the solution you'd like**
Add properties to the model to allow for more visual control

**Describe alternatives you've considered**
none

**Additional context**
This facilitates making the Google Sign In button the same size as the Sign in with Apple buttons for a more consistent UI.