Specify how script should be hashed in Plutus-core spec

Current plutus-core spec does not include how each scripts needs to be hashed(https://github.com/IntersectMBO/cardano-ledger/blob/master/eras/conway/impl/cddl-files/conway.cddl#L492). Script for each ledger language version needs to be hashed differently. It'd be nice to mention it in the spec since hashing uplc is rather important in Cardano and the spec mentions about ledger language anyways.