updating rust package documentation

crates/compiler/test_gen/Cargo.toml

@@ -4,6 +4,7 @@ version = "0.0.1"
 authors = ["The Roc Contributors"]
 license = "UPL-1.0"
 edition = "2021"
+description = "Contains all of Roc's code generation tests."
 
 [[test]]
 name = "test_gen"

crates/compiler/test_gen/src/lib.rs

@@ -1,2 +1,4 @@
+//! Contains all of Roc's [code generation](https://en.wikipedia.org/wiki/Code_generation_(compiler)) 
+//! tests.
 #[cfg(test)]
 pub mod helpers;