Add spring animation demo page

samples/RenderDemo/MainWindow.xaml

@@ -39,6 +39,9 @@
     <TabItem Header="Custom Animator">
       <pages:CustomAnimatorPage />
     </TabItem>
+    <TabItem Header="Spring Animation">
+      <pages:SpringAnimationsPage />
+    </TabItem>
     <TabItem Header="Clipping">
       <pages:ClippingPage />
     </TabItem>

samples/RenderDemo/Pages/SpringAnimationsPage.xaml

@@ -0,0 +1,35 @@
+<UserControl 
+  xmlns="https://github.com/avaloniaui" 
+  xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml" 
+  x:Class="RenderDemo.Pages.SpringAnimationsPage"
+  MaxWidth="600">
+  <UserControl.Resources>
+    <SpringEasing x:Key="SpringEasing" Mass="1" Stiffness="2000" Damping="20" InitialVelocity="0" />
+  </UserControl.Resources>
+  <UserControl.Styles>
+    <Style Selector="Border.spring">
+      <Style.Animations>
+        <Animation Duration="0:0:0.900" 
+                   IterationCount="Infinite" 
+                   PlaybackDirection="Normal" 
+                   Easing="{DynamicResource SpringEasing}">
+          <KeyFrame Cue="0%" KeySpline="">
+            <Setter Property="TranslateTransform.X" Value="-300"/>
+          </KeyFrame>
+          <KeyFrame Cue="100%">
+            <Setter Property="TranslateTransform.X" Value="0" />
+          </KeyFrame>
+        </Animation>
+      </Style.Animations>
+    </Style>
+  </UserControl.Styles>
+  <Grid>
+    <Border Classes="spring" Background="Red" Width="50" Height="50">
+      <Border.RenderTransform>
+        <TransformGroup>
+          <TranslateTransform />
+        </TransformGroup>
+      </Border.RenderTransform>
+    </Border>
+  </Grid>
+</UserControl>

samples/RenderDemo/Pages/SpringAnimationsPage.xaml.cs

@@ -0,0 +1,17 @@
+using Avalonia.Controls;
+using Avalonia.Markup.Xaml;
+
+namespace RenderDemo.Pages;
+
+public class SpringAnimationsPage : UserControl
+{
+    public SpringAnimationsPage()
+    {
+        InitializeComponent();
+    }
+
+    private void InitializeComponent()
+    {
+        AvaloniaXamlLoader.Load(this);
+    }
+}