CBOR value
Byte string
With type 'WrongType' if cbor is not a byte string
NOTE: decoded byte strings are zero-copy views aliasing the input
buffer - mutating the input after decoding (or mutating the returned
bytes) changes the other side. Call .slice() first if you need an
independent copy. This is deliberate: the zero-copy decode performance
profile is part of the library's contract.
Extract byte string value, throwing if type doesn't match.