example: add window_zoom example

examples/window_zoom.rs

@@ -14,7 +14,7 @@ fn app(cx: Scope) -> Element {
     cx.render(rsx! {
         input {
             r#type: "number",
-            value: "{level_display}",
+            value: "{level}",
             oninput: |e| {
                 level.set(e.value.parse::<f64>().unwrap_or_default())
             }