enhance: add TransitionMode prop for GrowlWindow.

src/Shared/HandyControl_Shared/Themes/Styles/Growl.xaml

@@ -60,6 +60,14 @@
                 </ControlTemplate>
             </Setter.Value>
         </Setter>
+        <Style.Triggers>
+            <Trigger Property="hc:Growl.TransitionMode" Value="Bottom2Top">
+                <Setter Property="Margin" Value="10,0,10,10"/>
+            </Trigger>
+            <Trigger Property="hc:Growl.TransitionMode" Value="Bottom2TopWithFade">
+                <Setter Property="Margin" Value="10,0,10,10"/>
+            </Trigger>
+        </Style.Triggers>
     </Style>
 
 </ResourceDictionary>