Review Button component

[henrialb]

There is a color variant in this component that is not intuitive, as the background colour is defined in the fill variant. Until now, there hadn't been the need for other background colours, but the navigation menu on mobile required it, so a quick fix was used, adding a new colour variant (buttonColor). We should review the variants of this component so that it becomes more intuitive to use. Compound variants should probably be used.