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

src/node_text_input.h

@@ -5,12 +5,15 @@
 class NodeTextInput : public NodeBorder
 {
 public:
+    float timer = 0;
     NodeText* m_text;
+    NodeBorder* m_cursor;
     std::string m_string;
     std::function<void(NodeTextInput*target)> on_return;
     virtual Node* clone_instantiate() const override;
     virtual void clone_finalize(Node* dest) const override;
     virtual void init() override;
+    virtual void on_tick(float dt) override;
     virtual kEventResult handle_event(Event* e) override;
     void init_controls();
     void set_text(const std::string& s);