Adding support for deriving serde Serialize and Deserialize on generated structs.

[slackers123]

Adding this would be helpful when trying to use the generated output of wgsl_to_wgpu as the types for a whole project.
I will try adding this in my own fork since it seems fairly simple.

Thank you for this amazing crate, and I hope my contribution is helpful.

[ScanMountGoat]

This could be a neat feature but should definitely be optional. You could add a derive_serde field to WriteOptions that defaults to false. This should be fairly simple to implement since a lot of the logic is already there for deriving bytemuck or encase.