[FR] - Provide comprehensive CDDL grammar for local tx-submission protocol

**External**

**Area**

*Other* Local tx submit mini protocol.

**Describe the feature you'd like**
We are using Local Tx submit mini protocol to submit transactions to the Cardano node, the mini protocol spec does not define the response CDDL as it is understood to be polymorphic. We want to parse the rejection message returned from the Cardano node, for which a CDDL spec would suffice.