create RTD badge

README.rst

@@ -1,6 +1,8 @@
 MSL-Qt
 ======
 
+|docs|
+
 This package provides custom Qt_ components that can be used for the user interface.
 
 Install
@@ -14,5 +16,10 @@ Alternatively, using the `MSL Package Manager`_ run::
 
    msl install qt
 
+.. |docs| image:: https://readthedocs.org/projects/msl-qt/badge/?version=latest
+   :target: http://msl-qt.readthedocs.io/en/latest/?badge=latest
+   :alt: Documentation Status
+   :scale: 100%
+
 .. _Qt: https://wiki.python.org/moin/PyQt
 .. _MSL Package Manager: http://msl-package-manager.readthedocs.io/en/latest/?badge=latest