Add module level documentation for prelude, models, and testing

src/lib.rs

@@ -134,6 +134,7 @@ pub mod maps;
 pub mod models;
 pub mod traits;
 
+/// Convenience re-exports of graph topology traits for common use.
 pub mod prelude {
     pub use crate::traits::{GraphTopology, GraphTopologyDeletion};
 }

src/models.rs

@@ -1,3 +1,5 @@
+//! Concrete graph topology models.
+
 pub mod append_graph;
 pub mod graph;
 

src/testing.rs

@@ -1,3 +1,5 @@
+//! Test fixture and test macros for graph topology and algorithm implementations.
+
 pub(crate) mod bfs_testing;
 pub(crate) mod dfs_testing;
 pub(crate) mod dijkstra_testing;