add scrollbar, improve presets, other small fixes

src/node_scroll.h

@@ -4,6 +4,7 @@
 class NodeScroll : public NodeBorder
 {
     bool m_dragging = false;
+    float m_scroll_dir = 1.f;
     glm::vec2 m_drag_start = glm::vec2(0);
     glm::vec2 m_offset_start = glm::vec2(0);
     glm::vec2 m_offset = glm::vec2(0);
@@ -12,5 +13,7 @@ public:
     NodeScroll();
     virtual Node* clone_instantiate() const override;
     virtual kEventResult handle_event(Event* e) override;
+    virtual void draw() override;
+    virtual void handle_resize(glm::vec2 old_size, glm::vec2 new_size) override;
     void fix_scroll();
 };