libdonet/readme: Reference link to libdonet.rs crate docs

Author: maxrdz

libdonet/README.md

@@ -3,3 +3,5 @@
 # libdonet
 
 The libdonet Rust library provides the necessary utilities and definitions for using the Donet networking protocol. These utilities include a lexer, parser, and high-level representation of the parsed DC file, as well as creating datagrams, iterating through datagrams, and the definition of every message type in the Donet protocol.
+
+The Rust crate documentation is available at [libdonet.rs](https://libdonet.rs).