Set main tab control background.

Author: Steve Ives

HarmonyCoreGenerator/View/MainWindow.xaml

@@ -64,7 +64,8 @@
 
         <TabControl
             Grid.Row="1"
-            SelectedIndex="{Binding SelectedTabIndex}">
+            SelectedIndex="{Binding SelectedTabIndex}"
+            Background="{DynamicResource {x:Static SystemColors.ControlBrushKey}}">
 
             <!-- TAB 0: SOLUTION INFO -->