GHSA-752W-5FWX-JX9F PyJWT accepts unknown `crit` header extensions

Summary 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 violates the MUST requirement in the RFC. This is t...