ux: style for search panel in text editor

Signed-off-by: leo <longshuang@msn.cn>

Author: love-linger

src/Resources/Styles.axaml

@@ -1414,6 +1414,7 @@
           <Grid RowDefinitions="Auto,Auto">
             <StackPanel Grid.Row="0" Orientation="Horizontal">
               <TextBox Watermark="{x:Static ae:SR.SearchLabel}"
+                       BorderBrush="{DynamicResource Brush.Border2}"
                        Name="PART_searchTextBox"
                        Width="265" Height="28"
                        Margin="0,0,0,0"