enhance: add HighlightTextBrush prop for HighlightTextBlock

src/Shared/HandyControl_Shared/Themes/Styles/TextBlock.xaml

@@ -1,4 +1,5 @@
 <ResourceDictionary xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
+                    xmlns:hc="clr-namespace:HandyControl.Controls"
                     xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml">
 
     <!--默认样式-->
@@ -49,4 +50,6 @@
     </Style>
     <Style x:Key="TextBlockDefaultBold" BasedOn="{StaticResource TextBlockBoldBaseStyle}" TargetType="TextBlock"/>
 
+    <Style BasedOn="{StaticResource HighlightTextBlockBaseStyle}" TargetType="hc:HighlightTextBlock"/>
+
 </ResourceDictionary>