Reduce includes

src/core/stylesheetloader.h

@@ -24,14 +24,15 @@
 
 #include "config.h"
 
-
 #include <QObject>
-#include <QWidget>
-#include <QEvent>
+#include <QPair>
 #include <QMap>
 #include <QPalette>
 #include <QString>
 
+class QWidget;
+class QEvent;
+
 class StyleSheetLoader : public QObject {
  public:
   explicit StyleSheetLoader(QObject *parent = nullptr);