add docs for the 'server' and 'storage' modules

taskchampion/src/storage/mod.rs

@@ -1,3 +1,12 @@
+/**
+
+This module defines the backend storage used by [`Replica`](crate::Replica).
+It defines a [trait](crate::storage::Storage) for storage implementations, and provides a default on-disk implementation as well as an in-memory implementation for testing.
+
+Typical uses of this crate do not interact directly with this module; [`StorageConfig`](crate::StorageConfig) is sufficient.
+However, users who wish to implement their own storage backends can implement the traits defined here and pass the result to [`Replica`](crate::Replica).
+
+*/
 use failure::Fallible;
 use std::collections::HashMap;
 use uuid::Uuid;