Create defaults for a nice circular button

[bitspittle]

Probably a CircleButton variant? Alternately, a CircleButton composable, which may be better if we start adding in size parameters to our widgets? (Since otherwise it might be hard to respond to different sizes)

Currently, if you clip with a Circle and set padding to 0.px, you get something where the button edges show slightly:

Anyway, if we support something official, then users won't have to worry about this.

I'm leaning towards making a CircleButton composable; it is readable and a bit more flexible for future changes.

[bitspittle]

Added to 1.0 because it should be trivial, and I think would be used very commonly.

[bitspittle]

Comment from Discord: Before adding a CircleButton, make sure something like clip(radius = 50.percent) doesn't work with multiple sizes.