Add ParseOption in order to skip claim validation in jwt.Parse method

I am trying to test my API's which are having different expiration time, so I had written my custom MiddlewareFunc. Claims will be validated in this custom function that's need to avoid validation in ParseWithClaims method.
If you approve this, I will make a PR for this.

Start by locating the jwt.Parse and ParseWithClaims entry points and read how claim validation is currently performed. Determine how a ParseOption could disable that validation while preserving the existing parsing behavior, then verify that custom middleware can perform the validation instead. Done means the requested option works without changing default validation.

Written by the indexing model from the issue text.