rect select for graph editor

ui/rectangleselect.cpp

@@ -0,0 +1,7 @@
+#include "rectangleselect.h"
+
+void draw_selection_rectangle(QPainter& painter, const QRect& rect) {
+	painter.setPen(QColor(204, 204, 204));
+	painter.setBrush(QColor(0, 0, 0, 32));
+	painter.drawRect(rect);
+}