docs: Link to cluster info

Can we get a link from this:
https://docs.determined.ai/latest/reference/experiment-config-reference.html#data
... that shows that they way to access the data is here:
https://docs.determined.ai/latest/reference/training/api-det-reference.html#determined.ClusterInfo.user_data

docs/reference/experiment-config-reference.rst

@@ -128,6 +128,8 @@ whatever configuration is needed for loading data for use by the experiment's mo
 example, if your experiment loads data from Amazon S3, the ``data`` field might contain the S3
 bucket name, object prefix, and AWS authentication credentials.
 
+See also: :ref:`det API Reference <det-reference>` > ``user_data`` property.
+
 ``workspace``
 =============