update: modify usestate to be borrowed

examples/readme.rs

@@ -9,13 +9,13 @@ fn main() {
 }
 
 fn app(cx: Scope) -> Element {
-    let mut count = use_state(&cx, || 0);
+    let count = use_state(&cx, || 0);
 
     cx.render(rsx! {
         div {
             h1 { "High-Five counter: {count}" }
-            button { onclick: move |_| count += 1, "Up high!" }
-            button { onclick: move |_| count -= 1, "Down low!" }
+            button { onclick: move |_| *count.modify() += 1, "Up high!" }
+            button { onclick: move |_| *count.modify() -= 1, "Down low!" }
         }
     })
 }