fix: farthest compare logic

[LeaVerou]

Hey, thanks! Which bug does this fix?

[caijf]

var max = Math.max(contrastOnBlack, contrastOnWhite);
// ...

return {
  // ...
  farthest: onWhite == max? _.WHITE : _.BLACK
}

onWhite == max The conditional judgment here is always no. I think it should be contrastOnWhite == max .