Reduce includes

src/core/standarditemiconloader.h

@@ -26,13 +26,13 @@
 #include <QtGlobal>
 #include <QObject>
 #include <QMap>
-#include <QString>
 #include <QImage>
-#include <QStandardItem>
-#include <QAbstractItemModel>
 
 #include "covermanager/albumcoverloaderoptions.h"
 
+class QAbstractItemModel;
+class QStandardItem;
+
 class Song;
 class AlbumCoverLoader;