feat:Redesign the usage pattern of WHAnimationHelper once more to deliver a superior axaml editing and consumption experience.

demo/Ursa.Demo/Pages/NavMenuDemo.axaml

@@ -8,6 +8,7 @@
     xmlns:u="https://irihi.tech/ursa"
     xmlns:vm="using:Ursa.Demo.ViewModels"
     xmlns:iri="https://irihi.tech/shared"
+    xmlns:views="using:Ursa.Demo.Pages"
     d:DesignHeight="450"
     d:DesignWidth="800"
     x:CompileBindings="True"
@@ -39,7 +40,10 @@
                 IsHorizontalCollapsed="{Binding #collapse.IsChecked, Mode=OneWay}"
                 ItemsSource="{Binding MenuItems}"
                 SelectedItem="{Binding SelectedMenuItem}"
-                SubMenuBinding="{Binding Children}">
+                SubMenuBinding="{Binding Children}"
+                u:WHAnimationHelper.TriggerAvaloniaProperty="{x:Static u:NavMenu.IsHorizontalCollapsedProperty}"
+                u:WHAnimationHelper.CreateAnimation="{x:Static views:NavMenuDemo.NavMenuAnimation}"
+                u:WHAnimationHelper.EnableWHAnimation="True">
                 <u:NavMenu.Styles>
                     <Style x:DataType="vm:MenuItem" Selector="u|NavMenuItem">
                         <Setter Property="IsSeparator" Value="{Binding IsSeparator}" />