Add animation panel action planner

src/node_panel_animation.h

@@ -10,6 +10,7 @@
 class Layer;
 
 namespace pp::app {
+struct DocumentAnimationPanelState;
 struct DocumentAnimationOperationPlan;
 }
 
@@ -73,6 +74,7 @@ class NodePanelAnimation : public Node
     float m_playback_timer = 0;
 
     void execute_animation_plan(const pp::app::DocumentAnimationOperationPlan& plan, Layer* layer = nullptr);
+    [[nodiscard]] pp::app::DocumentAnimationPanelState animation_panel_state() const;
 public:
     using this_class = NodePanelAnimation;
     using parent = Node;