Add more badges to readme

README.md

@@ -1,6 +1,6 @@
 <a href="https://dust3d.org" target="_blank"><image src="https://raw.githubusercontent.com/huxingyi/dust3d/master/dust3d-logo.png" width="66" height="58"></a>
 
-[![appveyor status](https://ci.appveyor.com/api/projects/status/github/huxingyi/dust3d?branch=master&svg=true)](https://ci.appveyor.com/project/huxingyi/dust3d) [![travis status](https://travis-ci.org/huxingyi/dust3d.svg?branch=master)](https://travis-ci.org/huxingyi/dust3d) [![readthedocs status](https://readthedocs.org/projects/dust3d/badge/?version=latest)](http://docs.dust3d.org/en/latest/?badge=latest)
+[![appveyor status](https://ci.appveyor.com/api/projects/status/github/huxingyi/dust3d?branch=master&svg=true)](https://ci.appveyor.com/project/huxingyi/dust3d) [![travis status](https://travis-ci.org/huxingyi/dust3d.svg?branch=master)](https://travis-ci.org/huxingyi/dust3d) [![readthedocs status](https://readthedocs.org/projects/dust3d/badge/?version=latest)](http://docs.dust3d.org/en/latest/?badge=latest) [![](https://img.shields.io/twitter/follow/jeremyhu2016.svg?label=%20%40jeremyhu2016&style=social)](https://twitter.com/jeremyhu2016) [![](https://img.shields.io/badge/Mailing%20List%20-Join-blue.svg)](https://www.freelists.org/list/dust3d) [![](https://img.shields.io/discourse/https/dust3d.discourse.group/status.svg)](https://dust3d.discourse.group/)
 
 Overview
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