add docs link to readme

Author: FoamyGuy

README.rst

@@ -78,6 +78,11 @@ This example demonstrates the library with the single built-in DotStar on the
     pixels = adafruit_dotstar.DotStar(board.APA102_SCK, board.APA102_MOSI, 1)
     pixels[0] = (10, 0, 0)
 
+Documentation
+=============
+
+API documentation for this library can be found on `Read the Docs <https://circuitpython.readthedocs.io/projects/dotstar/en/latest/>`_.
+
 Contributing
 ============