While implementing `ercp_basic.rs`, I have found some mistakes to fix: * [ ] Specify that [RFC 2119](https://datatracker.ietf.org/doc/html/rfc2119) is used to specify requirement levels * [ ] Add missing `Description*` commands to the table of content * [ ] Rename the *Type* field to *Code*, so it does not conflict with a reserved keyword in many languages * [ ] Add an `INTERNAL_ERROR` nack reason