docs: data messages documentation

proto/src/message/frontend.rs

@@ -4,6 +4,8 @@ use crate::message::primitive::pgstring::PgString;
 use crate::message::proto_message::ProtoMessage;
 use bincode::{Decode, Encode};
 
+/// Frontend messages sent from the client to the server.
+/// For more info visit the [`55.2.3. Message Formats`](https://www.postgresql.org/docs/current/protocol-message-formats.html)
 #[derive(Debug)]
 pub enum FrontendMessage {
     Query(QueryData),