three new color functions

I added 3 functions:
1 - invertluma( color ) > it inverts the luma of a given color
2 - contrastmore( color1, color2, minLumaDifference: 30% ) > if color1 and color2 have less than 30% of luma difference, it contrast a little bit more color2
3 - autocontrast( color1, color2, minLumaDifference) > similar than contrastmore, but if the new color2 have a luma more than 1 or less than 0, it inverts its luma value. Works better for example when color1 is the button background color, and color2 is the button text color.