refactor layout.h into single file per Node* classes

engine/node_viewport.h

@@ -0,0 +1,23 @@
+#pragma once
+#include "node.h"
+#include "shape.h"
+#include "texture.h"
+#include "event.h"
+
+class NodeViewport : public Node
+{
+public:
+    std::unique_ptr<ui::Plane> m_faces;
+    std::unique_ptr<Sampler> m_sampler;
+    uint16_t m_tex_id;
+    glm::vec2 drag_start;
+    glm::vec2 drag_end;
+    bool dragging = false;
+    float angle = 0.0f;
+    float angle_old;
+    
+    virtual void draw() override;
+    virtual Node* clone_instantiate() const override;
+    virtual void create() override;
+    virtual kEventResult handle_event(Event* e) override;
+};