more docs

Author: rmorshea

docs/source/javascript-modules.rst

@@ -113,7 +113,11 @@ While it's possible to implement a whole-sale replacement for IDOM's built-in cl
 adhering to IDOM's :ref:`API <Package API>` and :ref:`Specifications`, the easiest way
 to implement a custom client is to create an object that adheres to the
 :class:`~idom.client.protocol.ClientImplementation` protocol and update the ``current``
-value of the :attr:`~idom.client.protocol.client_implementation` ref.
+value of the :attr:`~idom.client.protocol.client_implementation` ref. An example of
+such an implementation can be seen in
+`IDOM's Jupyter Widgets <https://github.com/idom-team/idom-jupyter>`__.
+
+The following describes the client implementation interface:
 
 .. autoclass:: idom.client.protocol.ClientImplementation
     :noindex: