add docs link to readme

Author: FoamyGuy

README.rst

@@ -70,6 +70,11 @@ Usage Example
             pybadger.show_badge(name_string="Blinka", hello_scale=2, my_name_is_scale=2, name_scale=3)
 
 
+Documentation
+=============
+
+API documentation for this library can be found on `Read the Docs <https://circuitpython.readthedocs.io/projects/pybadger/en/latest/>`_.
+
 Contributing
 ============