Created by: bassjobsen
according to: #18119 (closed)
Some notices:
- I introduced $lightes-color and $darkest-color, see also #18118 (closed)
- using the color-contrast function means that some .bg variant got the lightest font whilst other got the darkest using brand colors. The same possible may happens for buttons. From the aesthetic point of view you possible prefer having all buttons the same font color. Accessibility tells you to do something different when not changing brand colors, also see: https://github.com/bassjobsen/bootstrap-a11y-theme
- i'm not sure how to attribute Compass for using the functions