Add basic methods into NavigatedPage

src/navigation.rs

@@ -320,6 +320,8 @@ macro_rules! state_navigate_handle {
 pub trait NavigatedPage<T> {
     fn navigate(&self, message: &T) -> Option<Page>;
     fn navigated(&mut self);
+    fn update(&mut self, message: T) -> Task<RootMessage>;
+    fn view(&self) -> Element<'_, T>;
 }
 
 pub trait KeyPressedPage {