Mention tokio-stream in SSE example

examples/sse/src/main.rs

@@ -50,6 +50,9 @@ async fn sse_handler(
     println!("`{}` connected", user_agent.as_str());
 
     // A `Stream` that repeats an event every second
+    //
+    // You can also create streams from tokio channels using the wrappers in
+    // https://docs.rs/tokio-stream
     let stream = stream::repeat_with(|| Event::default().data("hi!"))
         .map(Ok)
         .throttle(Duration::from_secs(1));