Consider adding a category for react-navigation


I was diving into react-navigation today and as of right now there are 296 Open issues, but most of them are just questions. I think it would help the maintainers a lot if they could send people to Stack Overflow and to this forum. Also this forum has a category for create-react-native-app which is also under the react-community organization on GitHub so a category for react-navigation seems like a good fit.