Add De-/Serialization Support

[teryror]

Most collection libraries support serialization, and for good reason. coca not supporting this is a pretty major drawback.

The two libraries I plan to support are

• serde: This is the most popular de-/serialization library in the Rust ecosystem, supporting it is just the polite thing to do.
• rkyv: This one has been building a user base quite rapidly, and it's the one I'm personally most likely to use after serde.