Integration with `colour` library

[georgefst]

Firstly, thanks! This is a really neat library. I have a draft of the same idea lying around somewhere, but I didn't get far with it. Yours is much better anyway, with the nice error messages, and little things like allowing non-alpha colours to have ff on the end (good because VSCode tends to insert them). I wouldn't have added named colours, or the & type synonym, but I guess neither of those things get in the way.

Anyway, given that Haskell does have a de facto standard colour library, would you consider adding first-class support for it?

The code is as simple as:

instance (IsWebColor s) => IsLabel s (Colour Double) where
    fromLabel = webColor @s \r g b -> sRGB24 r g b
instance (IsWebColorAlpha s) => IsLabel s (AlphaColour Double) where
    fromLabel = webColorAlpha @s \r g b a -> sRGB24 r g b `withOpacity` (fromIntegral a / 255)

And colour has no dependencies of its own beyond base, so it isn't much to take on.

[s-and-witch]

I apologise for the long silence - I forgot that GH requires notifications to be enabled explicitly and thought this project had received little to no attention from the community.

I don't think I want to add a dependency on any library that defines its own colors. There are multiple libraries that define their own colors and do not depend on colour: sdl2 and keid are two examples.

I may carry forward the discussion about introducing a dependency from the colour library to webcolor-labels - at the end of the day, libraries that define colors should be clients of this library, not the opposite.