Move dropdown button text and icon code to dropdown button class

include/gui/Utils.hpp

@@ -0,0 +1,13 @@
+#pragma once
+
+#include <mglpp/system/vec.hpp>
+#include <mglpp/graphics/Color.hpp>
+
+namespace mgl {
+    class Window;
+}
+
+namespace gsr {
+    // Inner border
+    void draw_rectangle_outline(mgl::Window &window, mgl::vec2f pos, mgl::vec2f size, mgl::Color color, float border_size);
+}