oatpp web-framework added to the list

Author: lganzzzo

README.md

@@ -707,6 +707,7 @@ array expressions, inspired by NumPy syntax. [BSD 3-clause] [website](http://qua
 * [Kore](https://kore.io/) - ultra fast and flexible web server / framework for web applications developed in C. [ISC]
 * [libOnion](http://www.coralbits.com/libonion/) - lightweight library to help you create webservers in C programming language. [LGPLv3]
 * [lwan](https://github.com/lpereira/lwan) - Experimental, scalable, high performance HTTP server. [GPL2]
+* [oat++](https://github.com/oatpp/oatpp) - Light, zero-dependency framework to create high-performance web-services. [Apache-2.0] [website](https://oatpp.io/) 
 * [Pistache](http://pistache.io/) - Pistache is a C++ REST framework written in pure C++11 with no external dependency. [Apache2]
 * [QDjango](https://github.com/jlaine/qdjango/) - A web framework written in C++ and built on top of the Qt library. Where possible it tries to follow django's API, hence its name. [LGPL]
 * [TreeFrog Framework](https://github.com/treefrogframework/treefrog-framework) - High-speed and full-stack web application framework based on C++ and Qt, which supports HTTP and WebSocket protocol (with O/R mapping). [BSD] [website](http://www.treefrogframework.org/)