Feature request: please add `invalid_result` deserializer

When dealing with [invalid data with serde](https://docs.rs/csv/latest/csv/tutorial/index.html#handling-invalid-data-with-serde), sometimes it is useful to get also invalid fields when present. The current [`invalid_option` deserializer](https://docs.rs/csv/latest/csv/fn.invalid_option.html) discards all invalid fields. It would be convenient to have a similar `invalid_result` deserializer, which returns `Ok(value)` for all valid fields, and `Err(string_field)` for all invalid fields.