Add a busy indicator to YACReaderTitledToolBar

It will be used in the libraries section to show that libraries are being updated in the background.

custom_widgets/yacreader_titled_toolbar.h

@@ -8,6 +8,7 @@
 #include <QPoint>
 
 class QIcon;
+class BusyIndicator;
 
 class DropShadowLabel : public QLabel
 {
@@ -38,9 +39,12 @@ public slots:
     void addAction(QAction *action);
     void addSpacing(int space);
     void addSepartor();
+    void showBusyIndicator();
+    void hideBusyIndicator();
 
 private:
     DropShadowLabel *nameLabel;
+    BusyIndicator *busyIndicator;
 };
 
 #endif // YACREADER_TITLED_TOOLBAR_H