New getting started with React Native docs!

I'm pleased to announce my first major contribution to React Nativenew introductory docs to help folks start their mobile development journey with React!

• How to use the docs: https://facebook.github.io/react-native/docs/next/getting-started
• Native & Core Components (with illustrations): https://facebook.github.io/react-native/docs/next/intro-react-native-components
• And a handy intro to React core concepts: https://facebook.github.io/react-native/docs/next/intro-react

Any feedback? I'm all ears!

Special thanks to Eli White, Dan Abramov, Christoph Nakazawa, Nader Dabit, Lorenzo, and Brent Vatne for their feedback and editorial assistance along the way and Kirsty Simmonds and Aasmund Eldhuset for proofreading and playtesting. And thanks of course to the countless contributors and community organizers who make React Native what it is today!