add 'scroll' container property

src/graphics/ui/elements/Container.cpp

@@ -226,6 +226,10 @@ void Container::refresh() {
     });
 }
 
+void Container::setScroll(int scroll) {
+    this->scroll = scroll;
+}
+
 const std::vector<std::shared_ptr<UINode>>& Container::getNodes() const {
     return nodes;
 }

src/graphics/ui/elements/Container.hpp

@@ -42,6 +42,7 @@ namespace gui {
         virtual int getScrollStep() const;
         virtual void setScrollStep(int step);
         virtual void refresh() override;
+        void setScroll(int scroll);
 
         virtual void mouseMove(GUI*, int x, int y) override;
         virtual void mouseRelease(GUI*, int x, int y) override;