Feature request: Add methods for converting HEX/RGB to HSLuv

[badfeather]

It would be very handy to have some methods to convert HEX or RGB to HSLuv colors in order to generate palettes based on brand colors for projects. As it is, I'm usually pasting the hex colors on the hsluv.org site to get the values, which is a bit tedious. Something like hsluv.fromHex([hex color]), hsluv.fromRGB([RGB color]), or if it can be automatically detected, hsluv.create([color]). Other color spaces like HSL might also be useful.

Thanks for working on the project. It's helped me generate accessible palettes for projects.