Add Serde support

[simonflick]

Implement Serde Serialize and Deserialize traits for Key and MouseButton as optional feature (like in the uuid crate).

[jD91mZM2]

Personal opinion: Why would you serialize a mouse button? 🤔

[simonflick]

Maybe it's too specific but I ask anyway, because it is very easy to implement. I use enigo to translate game controller input to mouse/keyboard input. The mapping just gets saved as a config file with serde wich is very pleasant. I wanted to use serde's remote derive feature, but apparently it doesn't work on enums. And even then, they don't implement the Clone trait, wich is also needed. I think it would be ok, to just implement Clone but Serde would be nice to have.

[jD91mZM2]

Yeah, I guess this is good. Let me make a pull request :)