feat: add avalonia basic ComboBox style.

src/Net_40/HandyControl_Net_40/Themes/Styles/Base/ComboBoxBaseStyle.xaml

@@ -2,7 +2,7 @@
                     xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
                     xmlns:hc="clr-namespace:HandyControl.Controls"
                     xmlns:system="clr-namespace:System;assembly=mscorlib">
-    
+
     <!--默认下拉框模板-->
     <ControlTemplate x:Key="ComboBoxTemplate" TargetType="ComboBox">
         <Grid>
@@ -478,7 +478,7 @@
                                 <Condition Property="IsSelected" Value="True"/>
                             </MultiTrigger.Conditions>
                             <Setter Property="Background" TargetName="Bd" Value="{DynamicResource PrimaryBrush}"/>
-                            <Setter Property="Foreground" Value="White"/>
+                            <Setter Property="Foreground" Value="{DynamicResource TextIconBrush}"/>
                         </MultiTrigger>
                     </ControlTemplate.Triggers>
                 </ControlTemplate>

src/Net_40/HandyControl_Net_40/Themes/Theme.xaml

@@ -5620,7 +5620,7 @@
 								<Condition Property="IsSelected" Value="True" />
 							</MultiTrigger.Conditions>
 							<Setter Property="Background" TargetName="Bd" Value="{DynamicResource PrimaryBrush}" />
-							<Setter Property="Foreground" Value="White" />
+							<Setter Property="Foreground" Value="{DynamicResource TextIconBrush}" />
 						</MultiTrigger>
 					</ControlTemplate.Triggers>
 				</ControlTemplate>