change twitter badge to mastodon

Author: freyfogle

README.md

@@ -10,7 +10,7 @@ A Python module to access the [OpenCage Geocoding API](https://opencagedata.com/
 [![Versions](https://img.shields.io/pypi/pyversions/opencage)](https://pypi.org/project/opencage/)
 ![GitHub contributors](https://img.shields.io/github/contributors/opencagedata/python-opencage-geocoder)
 [![Build Status](https://travis-ci.com/OpenCageData/python-opencage-geocoder.svg?branch=master)](https://travis-ci.com/OpenCageData/python-opencage-geocoder)
-[![Twitter Follow](https://img.shields.io/twitter/follow/OpenCage?label=Follow%20OpenCage&style=social)](https://twitter.com/opencage)
+![Mastodon Follow](https://img.shields.io/mastodon/follow/109287663468501769?domain=https%3A%2F%2Fen.osm.town%2F&style=social)
 
 ## Usage