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

src/app.cpp

@@ -442,6 +442,8 @@ void App::update(float dt)
     if (canvas && canvas->m_canvas)
         canvas->m_canvas->stroke_draw();
     
+    layout[main_id]->tick(dt);
+    
     if (!(redraw || animate))
         return;