Add split map example

examples/split_map.rs

@@ -0,0 +1,39 @@
+use futures::StreamExt;
+use split_stream_by::{Either, SplitStreamByMapExt};
+use tokio::join;
+
+#[derive(Debug)]
+struct Request {
+    //...
+}
+#[derive(Debug)]
+struct Response {
+    //...
+}
+#[derive(Debug)]
+enum Message {
+    Request(Request),
+    Response(Response),
+}
+
+#[tokio::main]
+async fn main() {
+    let incoming_stream = futures::stream::iter([
+        Message::Request(Request {}),
+        Message::Response(Response {}),
+        Message::Response(Response {}),
+    ]);
+
+    let (request_stream, response_stream) = incoming_stream.split_by_map(|item| match item {
+        Message::Request(req) => Either::Left(req),
+        Message::Response(res) => Either::Right(res),
+    });
+
+    let a = tokio::spawn(async {
+        println!("Requests: {:?}", request_stream.collect::<Vec<_>>().await);
+    });
+    let b = tokio::spawn(async {
+        println!("Responses: {:?}", response_stream.collect::<Vec<_>>().await);
+    });
+    let _ = join!(a, b);
+}