Pass style as argument to be able to calculate it at runtime

[LukasKalbertodt]

From https://github.com/LukasKalbertodt/bunt/issues/1#issuecomment-812863115:

Could the color and other styles be specified by argument? For example,

bunt::println!("{$*}error:{/$}", Color::Red, ty);

In that case I could calculate the color at runtime.