add tick and on_tick event, fix unsaved document prompt, implement TextInput blinking cursor

src/node_message_box.h

@@ -6,6 +6,7 @@
 class NodeMessageBox : public Node
 {
 public:
+    std::function<void(Node*)> on_submit = nullptr;
     Node* m_template;
     NodeButton* btn_ok;
     NodeButton* btn_cancel;
@@ -13,4 +14,5 @@ public:
     NodeText* m_title;
     virtual Node* clone_instantiate() const override;
     virtual void init() override;
+    virtual kEventResult handle_event(Event* e);
 };