Include documentation badge

Author: RedFantom

README.md

@@ -2,6 +2,7 @@
 [![Build Status](https://travis-ci.com/RedFantom/masterkeys-linux.svg?token=UBcv5ZyxSrELyQhSpadq&branch=master)](https://travis-ci.com/RedFantom/masterkeys-linux)
 [![License: GPL v3](https://img.shields.io/badge/License-GPL%20v3-blue.svg)](https://www.gnu.org/licenses/gpl-3.0)
 [![PyPI version](https://badge.fury.io/py/masterkeys.svg)](https://pypi.org/project/masterkeys/)
+[![Documentation](https://readthedocs.org/projects/masterkeys-linux/badge/?version=latest)](https://masterkeys-linux.readthedocs.io/en/latest)
 
 Cooler Master provides an SDK for its MasterKeys series of keyboards
 for use under Windows, but not for Linux. The SDK communicates with an

docs/index.rst

@@ -23,3 +23,6 @@ interface to the LEDs on the MasterKeys keyboard series.
 .. |PyPI| image:: https://badge.fury.io/py/masterkeys.svg
    :alt: PyPI Version
    :target: https://pypi.python.org/pypi/masterkeys
+.. |Docs| image:: https://readthedocs.org/projects/masterkeys-linux/badge/?version=latest
+   :alt: Documentation
+   :target: https://masterkeys-linux.readthedocs.io/en/latest