Code Quality: Add background to setting expanders (#17067)

Author: yaira2

src/Files.App/Views/Settings/AppearancePage.xaml

@@ -156,6 +156,7 @@
 					<GridView
 						Padding="8"
 						HorizontalAlignment="Stretch"
+						Background="{ThemeResource CardBackgroundFillColorDefaultBrush}"
 						ItemTemplate="{StaticResource AppThemeResourcesItemTemplate}"
 						ItemsSource="{x:Bind ViewModel.AppThemeResources, Mode=OneWay}"
 						SelectedItem="{x:Bind ViewModel.SelectedAppThemeResources, Mode=TwoWay}" />

src/Files.App/Views/Settings/DevToolsPage.xaml

@@ -55,7 +55,7 @@
 					ItemsSource="{x:Bind ViewModel.OpenInIDEOptions.Values}"
 					SelectedItem="{x:Bind ViewModel.SelectedOpenInIDEOption, Mode=TwoWay}" />
 				<wctcontrols:SettingsExpander.ItemsHeader>
-					<StackPanel Orientation="Vertical">
+					<StackPanel Background="{ThemeResource CardBackgroundFillColorDefaultBrush}" Orientation="Vertical">
 						<Grid
 							x:Name="IDEConfigGrid"
 							Padding="32,12"

src/Files.App/Views/Settings/GeneralPage.xaml

@@ -102,6 +102,7 @@
 					<Grid
 						Padding="8"
 						HorizontalAlignment="Stretch"
+						Background="{ThemeResource CardBackgroundFillColorDefaultBrush}"
 						RowSpacing="4"
 						Visibility="{x:Bind ViewModel.OpenASpecificPageOnStartup, Mode=OneWay}">
 						<Grid.RowDefinitions>

src/Files.App/Views/Settings/TagsPage.xaml

@@ -54,7 +54,7 @@
 
 				<Button Command="{x:Bind ViewModel.AddTagCommand, Mode=OneWay}" Content="{helpers:ResourceString Name=NewTag}" />
 				<wctcontrols:SettingsExpander.ItemsHeader>
-					<StackPanel>
+					<StackPanel Background="{ThemeResource CardBackgroundFillColorDefaultBrush}">
 						<!--  Create new tag  -->
 						<Grid
 							x:Name="AddTagGrid"