Discord Badge Added (Significant-Gravitas#760)

* Discord Badge 

Discord Badge added Issue Significant-Gravitas#749

* style changed

plastic style to flat style

README.md

@@ -4,6 +4,8 @@
 ![Python Version](https://img.shields.io/badge/3.7%20%7C%203.8%20%7C%203.9%20%7C%203.10-blue)
 [![Downloads](https://pepy.tech/badge/flaml)](https://pepy.tech/project/flaml)
 [![Join the chat at https://gitter.im/FLAMLer/community](https://badges.gitter.im/FLAMLer/community.svg)](https://gitter.im/FLAMLer/community?utm_source=badge&utm_medium=badge&utm_campaign=pr-badge&utm_content=badge)
+[![](https://img.shields.io/discord/1025786666260111483?logo=discord&style=flat)](https://discord.gg/Cppx2vSPVP)
+
 
 # A Fast Library for Automated Machine Learning & Tuning