Color modifiers

[m0ksem]

When I was adapting search filed for dark theme, I noticed that it has muted text colors and we're not able to change this colors with current colors.

Example:

I propose to extend color palette a bit with modifiers:
-shade-2
-shade-1
-tint-1
-tint-2

see Calculation method as reference

The problem here is that shade on white bg has bigger contrast that on dark bg...