Add Gitter badge

README.md

@@ -272,6 +272,6 @@ See [CONTRIBUTING.md](CONTRIBUTING.md) for contribution and pull request protoco
 
 ## License
 
-[![License: GPL v3.0](https://img.shields.io/badge/License-GPL%20v3-blue.svg)](https://www.gnu.org/licenses/gpl-3.0)
+[![License: GPL v3.0](https://img.shields.io/badge/License-GPL%20v3-blue.svg)](https://www.gnu.org/licenses/gpl-3.0) [![Join the chat at https://gitter.im/poanetwork/blockscout](https://badges.gitter.im/poanetwork/blockscout.svg)](https://gitter.im/poanetwork/blockscout?utm_source=badge&utm_medium=badge&utm_campaign=pr-badge&utm_content=badge)
 
 This project is licensed under the GNU General Public License v3.0. See the [LICENSE](LICENSE) file for details.