docs(readme): adding prettier badget

prettier instead standard badget

README.md

@@ -1,7 +1,7 @@
 # react-tooltip
 
 [![Version](http://img.shields.io/npm/v/react-tooltip.svg)](https://www.npmjs.org/package/react-tooltip)
-[![js-standard-style](https://img.shields.io/badge/code%20style-standard-brightgreen.svg?style=flat)](https://github.com/feross/standard)
+[![code style: prettier](https://img.shields.io/badge/code_style-prettier-ff69b4.svg)](https://github.com/prettier/prettier)
 [![npm download][download-image]][download-url]
 [![Build Status](https://travis-ci.org/wwayne/react-tooltip.svg?branch=master)](https://travis-ci.org/wwayne/react-tooltip)
 [![semantic-release](https://img.shields.io/badge/%20%20%F0%9F%93%A6%F0%9F%9A%80-semantic--release-e10079.svg)](https://github.com/semantic-release/semantic-release)