rename parent to m_parent and add floating panel class

src/node_panel_floating.h

@@ -0,0 +1,20 @@
+#pragma once
+#include "node_border.h"
+#include "node_button.h"
+
+class NodePanelFloating : public NodeBorder
+{
+    bool m_dragging = false;
+    glm::vec2 m_drag_start_pos;
+    glm::vec2 m_drag_start_cur;
+    NodeButton* m_button_minimize;
+public:
+    Node* m_container;
+    using this_class = NodePanelFloating;
+    using parent = NodeBorder;
+    virtual Node* clone_instantiate() const override;
+    virtual void clone_finalize(Node* dest) const override;
+    virtual kEventResult handle_event(Event* e) override;
+    virtual void init() override;
+    void init_controls();
+};