MAGETWO-66757: Add Crowdin badge - official translations #4501

 - Merge Pull Request #4501 from piotrekkaminski/magento2:readme-translations

Author: vrann

README.md

@@ -1,5 +1,6 @@
 [![Build Status](https://travis-ci.org/magento/magento2.svg?branch=develop)](https://travis-ci.org/magento/magento2)
 [![Gitter](https://badges.gitter.im/Join%20Chat.svg)](https://gitter.im/magento/magento2?utm_source=badge&utm_medium=badge&utm_campaign=pr-badge)
+[![Crowdin](https://d322cqt584bo4o.cloudfront.net/magento-2/localized.png)](https://crowdin.com/project/magento-2)
 <h2>Welcome</h2>
 Welcome to Magento 2 installation! We're glad you chose to install Magento 2, a cutting edge, feature-rich eCommerce solution that gets results.