pyjwt: PyJWT accepts unknown `crit` header extensions (RFC 7515 §4.1.11 MUST violation)

A missing verification step has been discovered in PyJWT. PyJWT does not validate the crit Critical Header Parameter defined in RFC 7515 §4.1.11. When a JWS token contains a crit array listing extensions that PyJWT does not understand, the library accepts the token instead of rejecting it. This...