message: implemnt 'q' to quit interactive tutorials
diff: GLFWOSPRayWindow *GLFWOSPRayWindow::activeWindow = nullptr;
  +static bool g_quitNextFrame = false;
  +
  GLFWOSPRayWindow::GLFWOSPRayWindow(const ospcommon::vec2i &windowSize,
  const ospcommon::box3f &worldBounds,
  OSPModel model,
  @@ -85,6 +87,9 @@ GLFWOSPRayWindow::GLFWOSPRayWindow(const ospcommon::vec2i &windowSize,
  case GLFW_KEY_G:
  activeWindow->showUi = !(activeWindow->showUi);
  break;
  + case GLFW_KEY_Q:
  + g_quitNextFrame = true;
  + break;
  }
  }
  });
  @@ -183,7 +188,7 @@ void GLFWOSPRayWindow::mainLoop()
  // continue until the user closes the window
  startNewOSPRayFrame();
  - while (!glfwWindowShouldClose(glfwWindow)) {
  + while (!glfwWindowShouldClose(glfwWindow) && !g_quitNextFrame) {
  ImGui_ImplGlfwGL3_NewFrame();
  display();
  