Serializing and deserializing rope with serde

Hello, I'm working on a project with crop running on WASM that requires serialization/deserialization with serde.

Would you be open to having the Serialize/Deserialize traits implemented in the crate directly?

I have a preliminary implementation at 43f984c which just serializes the rope as a string. I'm not sure if this a good way to do it, but it works.