Add TransitioningContentControl style support

Material.Styles/MaterialToolKit.xaml

@@ -79,6 +79,8 @@
     <!-- Custom controls (High-priority) -->
     <StyleInclude Source="avares://Material.Styles/SideSheet.xaml"/>
     
+    <StyleInclude Source="avares://Material.Styles/TransitioningContentControl.axaml"/>
+    
     <!-- DialogHost.Avalonia -->
     <!-- dialog host style have been removed for avoid unnecessary package linking -->
     <!-- you can still add it manually https://github.com/AvaloniaUtils/DialogHost.Avalonia -->

Material.Styles/TransitioningContentControl.axaml

@@ -0,0 +1,20 @@
+<Styles xmlns="https://github.com/avaloniaui"
+        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml" >
+    <Style Selector="TransitioningContentControl">
+        <!-- Set Defaults -->
+        <Setter Property="Template">
+            <ControlTemplate>
+                <ContentPresenter Name="PART_ContentPresenter"
+                                  Background="{TemplateBinding Background}"
+                                  BorderBrush="{TemplateBinding BorderBrush}"
+                                  BorderThickness="{TemplateBinding BorderThickness}"
+                                  CornerRadius="{TemplateBinding CornerRadius}"
+                                  ContentTemplate="{TemplateBinding ContentTemplate}"
+                                  Content="{TemplateBinding CurrentContent}"
+                                  Padding="{TemplateBinding Padding}"
+                                  VerticalContentAlignment="{TemplateBinding VerticalContentAlignment}"
+                                  HorizontalContentAlignment="{TemplateBinding HorizontalContentAlignment}"/>
+            </ControlTemplate>
+        </Setter>
+    </Style>
+</Styles>