Expand decode error to include information about error

[hellos3b]

Would be nice if the decode exception included information about the error instead of the error message, so the output could be formatted nicely to an end user

type path = array<string>
type expected = string
type actual = string

exception DecodeError(path, expected, actual)

The path property can point to where in an object or array that the error occured, so I can log a message like Expected "string" in Object.nested.field[0]