Ignore unknown CTAP response fields

[AlfioEmanueleFresta]

New versions of the specifications frequently add new fields. Ignoring new fields allow previous versions of the library not to fail when used with newer devices. See #65.

We may need to fork serde_indexed to add this functionality.

Includes:

• Allow unknown fields in numerically-indexed #[derive(DeserializeIndexed)] structs
  • See Allow unknown CBOR fields (ref #66) #110
• Allow unknown enum values, eg. unknown public key algorithms reported in GetInfo