chore: added gitter badge

Author: JohnstonCode

README.md

@@ -20,6 +20,8 @@
 [![Average time to resolve an issue](https://isitmaintained.com/badge/resolution/JohnstonCode/svn-scm.svg)](https://isitmaintained.com/project/JohnstonCode/svn-scm "Average time to resolve an issue")
 [![Percentage of issues still open](https://isitmaintained.com/badge/open/JohnstonCode/svn-scm.svg)](https://isitmaintained.com/project/JohnstonCode/svn-scm "Percentage of issues still open")
 
+[![Gitter chat](https://badges.gitter.im/gitterHQ/gitter.png)](https://gitter.im/svn-scm/Lobby)
+
 # Prerequisites
 
 > **Note**: This extension leverages your machine's SVN installation,\