Added an exmple how to use js bindings (#224)

* Added an exmple how to use js bindings

* rustmft

---------

Co-authored-by: Matthias Seitz <matthias.seitz@outlook.de>

examples/js-binding-listener.rs

@@ -0,0 +1,50 @@
+use chromiumoxide::browser::{Browser, BrowserConfig};
+use chromiumoxide_cdp::cdp::js_protocol::runtime::{AddBindingParams, EventBindingCalled};
+use futures::StreamExt;
+use std::sync::Arc;
+use tokio::sync::Mutex;
+
+#[tokio::main]
+async fn main() -> Result<(), Box<dyn std::error::Error>> {
+    tracing_subscriber::fmt::init();
+
+    let (mut browser, mut handler) =
+        Browser::launch(BrowserConfig::builder().with_head().build()?).await?;
+
+    let handle = async_std::task::spawn(async move {
+        while let Some(h) = handler.next().await {
+            match h {
+                Ok(_) => continue,
+                Err(_) => break,
+            }
+        }
+    });
+
+    let page = browser.new_page("about:blank").await?;
+
+    let mut listener = page.event_listener::<EventBindingCalled>().await?;
+
+    let value_from_js: Arc<Mutex<String>> = Arc::new(Mutex::new("".to_string()));
+    let value_from_js_clone = Arc::clone(&value_from_js);
+
+    tokio::spawn(async move {
+        while let Some(event) = listener.next().await {
+            if event.name == "testFunc1" {
+                let mut locked_value = value_from_js_clone.lock().await;
+                *locked_value = event.payload.clone();
+            }
+        }
+    });
+
+    page.execute(AddBindingParams::new("testFunc1")).await?;
+
+    page.evaluate("window.testFunc1('30');").await?;
+
+    let value = value_from_js.lock().await;
+    assert_eq!(*value, "30");
+
+    browser.close().await?;
+    handle.await;
+
+    Ok(())
+}