Add accessible name to Control Alt Fill checkbox on Colors page (#785)

The example checkbox in the 'Control Alt Fill' section of the WPF Gallery Colors page had no AutomationProperties.Name, so Narrator announced only its checked state and not its label. Adding an accessible name fixes the MAS 4.1.2 (Name, Role, Value) issue.

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Author: mmanolova-msft

Sample Applications/WPFGallery/Views/DesignGuidance/FillSection.xaml

@@ -96,7 +96,7 @@
             Title="Control Alt Fill"
             Background="{DynamicResource SolidBackgroundFillColorQuarternaryBrush}"
             Description="Fill used for the 'off' states of toggle controls">
-            <CheckBox Focusable="False"/>
+            <CheckBox Focusable="False" AutomationProperties.Name="Control Alt Fill"/>
         </controls:ColorPageExample>
         <Border Style="{StaticResource ColorTilesPanelStyle}" Margin="0,8"><Grid>
             <Grid.ColumnDefinitions>