👷 added Codacy badge

README.md

@@ -4,6 +4,7 @@
 [![Build Status](https://ci.appveyor.com/api/projects/status/1acb366xfyg3qybk/branch/develop?svg=true)](https://ci.appveyor.com/project/nlohmann/json)
 [![Coverage Status](https://img.shields.io/coveralls/nlohmann/json.svg)](https://coveralls.io/r/nlohmann/json)
 [![Coverity Scan Build Status](https://scan.coverity.com/projects/5550/badge.svg)](https://scan.coverity.com/projects/nlohmann-json)
+[![Codacy Badge](https://api.codacy.com/project/badge/Grade/f3732b3327e34358a0e9d1fe9f661f08)](https://www.codacy.com/app/nlohmann/json?utm_source=github.com&utm_medium=referral&utm_content=nlohmann/json&utm_campaign=Badge_Grade)
 [![Try online](https://img.shields.io/badge/try-online-blue.svg)](http://melpon.org/wandbox/permlink/4NEU6ZZMoM9lpIex)
 [![Documentation](https://img.shields.io/badge/docs-doxygen-blue.svg)](http://nlohmann.github.io/json)
 [![GitHub license](https://img.shields.io/badge/license-MIT-blue.svg)](https://raw.githubusercontent.com/nlohmann/json/master/LICENSE.MIT)