Add an async stream demo

rust-exercises.code-workspace

@@ -1,5 +1,8 @@
 {
     "folders": [
+        {
+            "path": "./stream-composition"
+        },
         {
             "path": "./async-streams"
         },

stream-composition/Cargo.toml

@@ -0,0 +1,7 @@
+[package]
+name = "stream-composition"
+version = "0.1.0"
+edition = "2024"
+
+[dependencies]
+trpl = "0.2.0"

stream-composition/src/main.rs

@@ -0,0 +1,22 @@
+use trpl::{ReceiverStream, Stream, StreamExt};
+
+fn main() {
+    trpl::run(async {
+        let mut messages = get_messages();
+
+        while let Some(message) = messages.next().await {
+            println!("{message}");
+        }
+    });
+}
+
+fn get_messages() -> impl Stream<Item = String> {
+    let (tx, rx) = trpl::channel();
+
+    let messages = ["a", "b", "c", "d", "e", "f", "g", "h", "i", "j"];
+    for message in messages {
+        tx.send(format!("Message: '{message}'")).unwrap();
+    }
+
+    ReceiverStream::new(rx)
+}