set option to select higlighted text color

keep it independent from background color, should make it easier to add a color section option to branding

src/calamares/progresstree/ProgressTreeDelegate.cpp

@@ -135,7 +135,7 @@ ProgressTreeDelegate::paintViewStep( QPainter* painter,
 
     if ( isCurrent )
     {
-        painter->setPen( CalamaresStyle::SIDEBAR_BACKGROUND );
+        painter->setPen( CalamaresStyle::SIDEBAR_TEXT_SELECT );
         painter->setBrush( APP->mainWindow()->palette().background() );
     }
 

src/libcalamaresui/utils/CalamaresStyle.h

@@ -28,6 +28,7 @@ namespace CalamaresStyle {
 
 static const QColor SIDEBAR_BACKGROUND =  "#292F34";
 static const QColor SIDEBAR_TEXT =        "#FFFFFF";
+static const QColor SIDEBAR_TEXT_SELECT = "#292F34";
 
 } // namespace CalamaresStyle