One layer of API indexes rather than 2.

Author: Julian

docs/api/index.rst

@@ -1,7 +1,22 @@
 API Reference
 =============
 
+Submodules
+----------
+
 .. toctree::
    :titlesonly:
 
-   /api/jsonschema/index
+   /api/jsonschema/exceptions/index
+   /api/jsonschema/protocols/index
+   /api/jsonschema/validators/index
+
+:mod:`jsonschema`
+-----------------
+
+.. automodule:: jsonschema
+   :members:
+   :imported-members:
+   :exclude-members: Validator
+
+.. autodata:: jsonschema._format._F