More docs on protocol module

src/protocol.rs

@@ -1,6 +1,17 @@
 //! Provides low-level access to the Minecraft protocol.
 //!
-//! You should avoid this module if possible.
+//! Contained within are the definitions of Minecraft's [`packets`] and the
+//! [`codec`] module for performing packet IO.
+//!
+//! While the protocol module is technically public API, its use is discouraged
+//! and has thus been hidden from the documentation. You may find yourself
+//! needing to use this module under the following circumstances:
+//! - You want to send packets to clients manually using the [`send_packet`]
+//!   function.
+//! - You are writing a proxy between the client and server.
+//! - You are writing a Minecraft client.
+//!
+//! [`send_packet`]: crate::client::Client::send_packet
 
 use std::io::{Read, Write};
 use std::mem;