docs: add prettier badge

README.md

@@ -1,4 +1,4 @@
-## react-native-drawer-layout [![CircleCI](https://circleci.com/gh/react-native-community/react-native-drawer-layout/tree/master.svg?style=svg)](https://circleci.com/gh/react-native-community/react-native-drawer-layout/tree/master)
+## react-native-drawer-layout [![CircleCI](https://circleci.com/gh/react-native-community/react-native-drawer-layout/tree/master.svg?style=svg)](https://circleci.com/gh/react-native-community/react-native-drawer-layout/tree/master) [![styled with prettier](https://img.shields.io/badge/styled_with-prettier-ff69b4.svg)](https://github.com/prettier/prettier)
 
 A platform-agnostic drawer layout. It uses a pure JavaScript implementation on every platform to ensure consistency. We try to keep it up to date with the implementation of [DrawerLayoutAndroid](https://facebook.github.io/react-native/docs/drawerlayoutandroid.html#content) and add features we see as necessary too.