chore: optimized element layout of extend controls demo

src/Shared/HandyControlDemo_Shared/UserControl/Controls/ImageBrowserDemoCtl.xaml

@@ -8,7 +8,7 @@
              xmlns:hc="https://handyorg.github.io/handycontrol">
     <hc:TransitioningContentControl>
         <StackPanel Margin="32">
-            <hc:ImageViewer Background="{DynamicResource SecondaryRegionBrush}" Width="600" Height="330" ImageSource="/HandyControlDemo;component/Resources/Img/1.jpg"/>
+            <hc:ImageViewer Background="{DynamicResource SecondaryRegionBrush}" MaxWidth="600" Height="330" ImageSource="/HandyControlDemo;component/Resources/Img/1.jpg"/>
             <Button Margin="0,32,0,0" Command="{Binding OpenImgCmd}" Content="{ex:Lang Key={x:Static langs:LangKeys.OpenImageBrowser}}" Style="{StaticResource ButtonPrimary}" HorizontalAlignment="Center"/>
         </StackPanel>
     </hc:TransitioningContentControl>