Code Quality: Prevent filter header from stealing focus

Author: yaira2

src/Files.App/Views/Shells/ModernShellPage.xaml

@@ -130,6 +130,7 @@
 			Padding="26,8,12,8"
 			BorderBrush="{ThemeResource DividerStrokeColorDefaultBrush}"
 			BorderThickness="0,0,0,1"
+			IsTabStop="False"
 			Visibility="{x:Bind ShellViewModel.ShowFilterHeader, Mode=OneWay}">
 			<StackPanel
 				VerticalAlignment="Center"
@@ -158,7 +159,8 @@
 			x:Name="ItemDisplayFrame"
 			Grid.Row="2"
 			x:FieldModifier="public"
-			Navigated="ItemDisplayFrame_Navigated" />
+			Navigated="ItemDisplayFrame_Navigated"
+			TabIndex="1" />
 
 		<VisualStateManager.VisualStateGroups>
 			<VisualStateGroup x:Name="ShellBorderFocusState">