Add jsonschema ref to PEP 426

pep-0426.txt

@@ -451,7 +451,11 @@ Metadata validation
 -------------------
 
 A `jsonschema <https://pypi.python.org/pypi/jsonschema>`__ description of
-the defined metadata schema will be provided prior to PEP acceptance.
+the distribution metadata is `available
+<http://hg.python.org/peps/file/default/pep-0426/pymeta-schema.json>`__.
+
+This schema does NOT currently handle validation of some of the more complex
+string fields (instead treating them as opaque strings).
 
 Except where otherwise noted, all URL fields in the metadata MUST comply
 with RFC 3986.