Add full readme to crate documentation

src/lib.rs

@@ -6,7 +6,7 @@
 )]
 #![deny(missing_docs)]
 
-//! A crate to run the Rust compiler (or other binaries) and test their command line output.
+#![cfg_attr(doc, doc = include_str!("../README.md"))]
 
 use build_manager::BuildManager;
 pub use color_eyre;