Fluent: Add NotificationCard missed resources (same as in Default theme)

src/Avalonia.Themes.Fluent/Accents/FluentControlResourcesDark.xaml

@@ -437,6 +437,15 @@
     <StaticResource x:Key="CalendarViewCalendarItemRevealBorderBrush" ResourceKey="SystemControlTransparentRevealBorderBrush" />
     <StaticResource x:Key="CalendarViewNavigationButtonBorderBrushPointerOver" ResourceKey="SystemControlHighlightTransparentBrush" />
     <StaticResource x:Key="CalendarViewNavigationButtonBorderBrush" ResourceKey="SystemControlTransparentBrush" />
+    
+    <!--Resources for NotificationCard.xaml -->
+    <SolidColorBrush x:Key="NotificationCardBackgroundBrush" Color="#444444" Opacity="0.75"/>
+    <SolidColorBrush x:Key="NotificationCardProgressBackgroundBrush" Color="#9A9A9A" />
+    <SolidColorBrush x:Key="NotificationCardInformationBackgroundBrush" Color="#007ACC" Opacity="0.75"/>
+    <SolidColorBrush x:Key="NotificationCardSuccessBackgroundBrush" Color="#1F9E45" Opacity="0.75"/>
+    <SolidColorBrush x:Key="NotificationCardWarningBackgroundBrush" Color="#FDB328" Opacity="0.75"/>
+    <SolidColorBrush x:Key="NotificationCardErrorBackgroundBrush" Color="#BD202C" Opacity="0.75"/>
+    
     <!-- Resources for RadioButton.xaml -->
     <x:Double x:Key="RadioButtonBorderThemeThickness">1</x:Double>
     <StaticResource x:Key="RadioButtonForeground" ResourceKey="SystemControlForegroundBaseHighBrush" />