some refractoring and dataholder

src/examples.rs

@@ -3,8 +3,16 @@ use crate::prelude::*;
 pub fn examples() -> Element {
     rsx! {
         styling: Some(styling()),
-        if (2 == 2) {
-            rsx_elem! { button { class: "btn", "Hello, World!" } }
+        button { class: "btn", on_click: Handler::new(|btn: &mut Button, _, document| {
+            let data = document.get_element_by_id::<DataHolder<'_, String>>("my_data").unwrap();
+            data.data += "!";
+            btn.children.set_text(&data.data);
+        }), "Hello, World!" }
+
+        {
+            let mut data = dataholder::<String>();
+            data.id = "my_data";
+            data
         }
     }
 }