Update README.md

Author: fanvanzh

README.md

@@ -1,5 +1,6 @@
 # 3dtiles
 
+[![glTF status](https://img.shields.io/badge/glTF-2%2E0-green.svg?style=flat)](https://github.com/KhronosGroup/glTF)
 [![Build status](https://ci.appveyor.com/api/projects/status/lyhf989tnt9jhi9y?svg=true)](https://ci.appveyor.com/project/fanvanzh/3dtiles)
 
 The fastest tools for 3dtiles convert in the world!