feat: add gitter chat badge

Author: sanjayankur31

README.md

@@ -11,6 +11,7 @@ pyNeuroML
 [![Documentation Status](https://readthedocs.org/projects/pyneuroml/badge/?version=latest)](https://pyneuroml.readthedocs.io/en/latest/?badge=latest)
 [![GitHub Org's stars](https://img.shields.io/github/stars/NeuroML?style=social)](https://github.com/NeuroML)
 [![Twitter Follow](https://img.shields.io/twitter/follow/NeuroML?style=social)](https://twitter.com/NeuroML)
+[![Gitter](https://badges.gitter.im/NeuroML/community.svg)](https://gitter.im/NeuroML/community?utm_source=badge&utm_medium=badge&utm_campaign=pr-badge)
 
 A single package in Python unifying scripts and modules for reading, writing, simulating and analysing NeuroML2/LEMS models.