Boston Children’s Museum has launched a new app designed to help youngsters learn more about Asian cultures. The museum says its ‘‘League of Extraordinary Bloggers’’ app will complement five children’s museum traveling exhibits devoted to China, Japan, Korea, and Vietnam. Children’s Museum senior vice president Leslie Swartz said Asia is becoming increasingly important and it’s ‘‘vitally important’’ to find new ways for young people to learn more about each other. The app introduces teen agents from each country, and together they attempt to solve a mission. In the course of the game, users explore the capital cities and learn about the key sites, languages, and currencies. Children’s museums in Houston, New York, St. Louis, Missouri, and San Jose, Calif., contributed content and advice for the app.