[Enhancement] Add DecodingError as associated type in decode enum case in ResponseError

[gentilijuanmanuel]

Hello! I'm using this package for a side project, so thank you for open sourcing it 🙂

This PR is a proposal to add Swift.DecodingError as an associated value in the .decode enum case in ResponseError. The reason: sometimes, when you're debugging an API call with lots of properties and sub-objects, is useful to inspect the Xcode Console and see which property doesn't have the correct type. Without exposing Swift.DecodingError, this ability is hidden by the package.

It's just a proposal so feel free to close it if you don't consider it's applicable for your package!

[mdb1]

LGTM! Thanks for this addition 🚀. I've written a custom Logger for decoding errors in the past, I'll try to find it and add it to the library if I do.