wip: add use_callback hook

examples/callback.rs

@@ -0,0 +1,20 @@
+use std::rc::Rc;
+
+use dioxus::prelude::*;
+
+fn main() {
+    dioxus_desktop::launch(app);
+}
+
+fn app(cx: Scope) -> Element {
+    let login = use_callback!(cx, || |evt| async {
+        //
+    });
+
+    cx.render(rsx! {
+        button {
+            onclick: login,
+            "Click me!"
+        }
+    })
+}