chore: adjusted the project directory structure

app/toolbutton.h

@@ -0,0 +1,20 @@
+#ifndef TOOLBUTTON_H
+#define TOOLBUTTON_H
+
+#include <QPushButton>
+
+class OpacityHelper;
+class ToolButton : public QPushButton
+{
+    Q_OBJECT
+public:
+    ToolButton(bool hoverColor = false, QWidget * parent = nullptr);
+
+public slots:
+    void setOpacity(qreal opacity, bool animated = true);
+
+private:
+    OpacityHelper * m_opacityHelper;
+};
+
+#endif // TOOLBUTTON_H