Hardcode font settings in WindowController

To to make sure we have a predictable base font.

Author: Steven Kirk

src/GitHub.VisualStudio/UI/WindowController.xaml

@@ -15,6 +15,11 @@
         HasMinimizeButton="False"
         HasMaximizeButton="False"
         Background="White"
+        FontFamily="Segoe UI"
+        FontSize="12"
+        FontStretch="Normal"
+        FontStyle="Normal"
+        FontWeight="Normal"
         SnapsToDevicePixels="True"
         UseLayoutRounding="True">
     <Grid x:Name="Container">