Buttons variants

Buttons
https://vanillaframework.io/docs/patterns/buttons

We currently have a very limited set of colors we can use for buttons, which is good for sites, but very limiting for more complex apps.

To show hierarchy and signal meaning we would need Default button also in red (negative) and blue (link color), including the icon color.


Start with the Buttons documentation at https://vanillaframework.io/docs/patterns/buttons and compare it with the current button styles. Trace how the Default button and its icon color are defined, then add red negative and blue link-color variants; done means both variants render with matching icon colors and are represented in the documentation.

Written by the indexing model from the issue text.