combobox item padding.

src/Avalonia.Themes.Fluent/ComboBoxItem.xaml

@@ -1,9 +1,25 @@
 <Styles xmlns="https://github.com/avaloniaui">
+  <Design.PreviewWith>
+    <Border Padding="20">
+      <StackPanel Spacing="10">
+        <ComboBox>
+          <ComboBoxItem>Item 1</ComboBoxItem>
+          <ComboBoxItem>Item 2</ComboBoxItem>
+        </ComboBox>
+
+        <ComboBox IsEnabled="False">
+          <ComboBoxItem>Item 1</ComboBoxItem>
+          <ComboBoxItem>Item 2</ComboBoxItem>
+        </ComboBox>
+      </StackPanel>
+    </Border>
+  </Design.PreviewWith>
+  
   <Style Selector="ComboBoxItem">
-    <Setter Property="Background" Value="Transparent"/>
-    <Setter Property="Padding" Value="2"/>
-    <Setter Property="HorizontalAlignment" Value="Stretch"/>
-    <Setter Property="HorizontalContentAlignment" Value="Left"/>
+    <Setter Property="TextBlock.Foreground" Value="{DynamicResource ComboBoxItemForeground}" />
+    <Setter Property="Background" Value="{DynamicResource ComboBoxItemBackground}" />    
+    <Setter Property="Padding" Value="{DynamicResource ComboBoxItemThemePadding}" />
+    <Setter Property="HorizontalContentAlignment" Value="Stretch" />    
     <Setter Property="Template">
       <ControlTemplate>
         <ContentPresenter Name="PART_ContentPresenter"