[Image Resizer] Added AutomationProperties.HelpText to dimensions combo-box (#37122)

Co-authored-by: Stefan Markovic <stefan@janeasystems.com>

src/modules/imageresizer/ui/App.xaml

@@ -14,6 +14,7 @@
             </ResourceDictionary.MergedDictionaries>
 
             <v:SizeTypeToVisibilityConverter x:Key="SizeTypeToVisibilityConverter" />
+            <v:SizeTypeToHelpTextConverter x:Key="SizeTypeToHelpTextConverter" />
             <v:EnumValueConverter x:Key="EnumValueConverter" />
             <v:AutoDoubleConverter x:Key="AutoDoubleConverter" />
             <v:BoolValueConverter x:Key="BoolValueConverter" />