Add stubs for the page on device.

Author: Diptorup Deb

docs/docfiles/user_guides/manual/dpctl/devices.rst

@@ -13,7 +13,7 @@ The :class:`dpctl.SyclDevice` class is an abstract representation of a
 data-parallel computation device. A device can be a CPU, GPU, FPGA, or other
 type of accelerator.
 
-Listing devices
+Listing Devices
 ---------------
 
 .. todo::

docs/docfiles/user_guides/manual/dpctl/platforms.rst

@@ -11,6 +11,9 @@ platforms queryable using dpctl depends on the device drivers that are installed
 on a system. A single driver may control multiple physical XPU, thus a platform
 may also consist of multiple XPUs.
 
+Listing Available Platforms
+---------------------------
+
 The platforms available on a system can be queried using the
 :func:`dpctl.lsplatform` function. In addition, as illustrated in the following
 example it is possible to print out metadata about a platform.