Add constants.rst for documenting dpctl constants

Also adds custom formatting for Enums into `index.rst`

Author: ndgrigorian

docs/doc_sources/api_reference/dpctl/constants.rst

@@ -0,0 +1,16 @@
+.. _dpctl_constants:
+
+Constants
+========================
+
+The following constants are defined in :py:mod:`dpctl`:
+
+.. currentmodule:: dpctl
+
+.. autodata:: backend_type
+
+.. autodata:: device_type
+
+.. autodata:: event_status_type
+
+.. autodata:: global_mem_cache_type

docs/doc_sources/api_reference/dpctl/index.rst

@@ -64,14 +64,17 @@
 
 .. rubric:: Enums
 
-.. autosummary::
-    :toctree: generated
-    :nosignatures:
+.. list-table::
+    :widths: 10 50
 
-    device_type
-    backend_type
-    event_status_type
-    global_mem_cache_type
+    * - :py:class:`dpctl.device_type`
+      - An :class:`enum.Enum` of supported SYCL device types.
+    * - :py:class:`dpctl.backend_type`
+      - An :class:`enum.Enum` of supported SYCL backends.
+    * - :py:class:`dpctl.event_status_type`
+      - An :class:`enum.Enum` of SYCL event states.
+    * - :py:class:`dpctl.global_mem_cache_type`
+      - An :class:`enum.Enum`  of global memory cache types for a device.
 
 .. rubric:: Exceptions