Settings: Fix theme preview

Author: TBM13

Flow.Launcher/SettingPages/Views/SettingsPaneTheme.xaml

@@ -313,6 +313,9 @@
                                 Width="400"
                                 Margin="40 30 0 10"
                                 SnapsToDevicePixels="True"
+                                Background="{DynamicResource Color01B}"
+                                BorderBrush="{DynamicResource SystemThemeBorder}"
+                                BorderThickness="1"
                                 Style="{DynamicResource PreviewWindowBorderStyle}">
                                 <Border BorderThickness="0" Style="{DynamicResource WindowRadius}">
                                     <Grid>