Support for serde (de)serialization of color types

[mitchmindtree]

I'm currently using palette in a downstream crate where I'd like to allow the user to serialize and deserialize custom Themes - a set of styling defaults including some color types from palette. I'm hoping to avoid writing custom implementations of the serde traits in favour of adding the necessary derives to palette itself where others may also find this useful. Perhaps this could be added as an opt-in feature similarly to cgmath, petgraph and others do?

[Ogeon]

Yes, absolutely! It should probably be quite straight forward to add and doing it behind a feature sounds like a good plan.

[Ogeon]

I'm adding this in #90. It will be just straight (de)serialization without anything too fancy. The only exceptions are the alpha types that will be flattened, so a JSON serialization of RGB with transparency will be {"red":0.1,"green":0.2,"blue":0.3,"alpha":0.4}.

Let me know if any of this doesn't work with your use case and maybe we can tweak it a bit. If you need other field names or a non-struct format, I would recommend creating a custom types for those representations and convert to and from palette types.

[Ogeon]

To clarify: it's fine to reopen or continue the conversation even after it's merged. 🙂