Update README file of websocket example

examples/websocket/README.md

@@ -2,7 +2,10 @@
 
 A simple example that keeps a WebSocket connection open to an echo server.
 
-The __[`main`]__ file contains all the code of the example.
+The example consists of 3 modules:
+- [`main`] contains the `Application` logic.
+- [`echo`] implements a WebSocket client for the [`echo::server`] with `async-tungstenite`.
+- [`echo::server`] implements a simple WebSocket echo server with `warp`.
 
 You can run it with `cargo run`:
 ```
@@ -10,3 +13,5 @@ cargo run --package websocket
 ```
 
 [`main`]: src/main.rs
+[`echo`]: src/echo.rs
+[`echo::server`]: src/echo/server.rs