Serde support

[volks73]

I was starting to play around with this crate and others in the "ndarray family" to become more familiar with using Rust for CV and ML applications. In my adventure, I have a need to (de)serialize images to pass between processes. Constantly decoding/encoding into an image format seems excessive, but maybe this is the ultimate solution. So, I saw that the ndarray crate has an optional serde feature, but the core, ImageBase type in this crate does not implement the Serialize or Deserialize traits and there is no similar optional feature.

Is there interest in adding Serde support to this crate as a similar optional feature so ImageBase can be (de)serialized?

[xd009642]

Sure, such a PR would be accepted (add serde as a feature that optionally enables ndarray serde feature).