Add info for rotaryio

Author: tekktrik

shared-bindings/rotaryio/__init__.c

@@ -39,6 +39,9 @@
 //| `Wikipedia's Rotary Encoder page <https://en.wikipedia.org/wiki/Rotary_encoder>`_ for more
 //| background.
 //|
+//| For more information on working with rotary encoders using this library, see
+//| `this Learn Guide <https://learn.adafruit.com/rotary-encoder>`_.
+//|
 //| All classes change hardware state and should be deinitialized when they
 //| are no longer needed if the program continues after use. To do so, either
 //| call :py:meth:`!deinit` or use a context manager. See