libnvdimm, MAINTAINERS: Maintainer Entry Profile

Document the basic policies of the libnvdimm subsystem and provide a first
example of a Maintainer Entry Profile for others to duplicate and edit.

Cc: Vishal Verma <vishal.l.verma@intel.com>
Cc: Dave Jiang <dave.jiang@intel.com>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>
Link: https://lore.kernel.org/r/157462919825.1729495.5877405723948988416.stgit@dwillia2-desk3.amr.corp.intel.com


Signed-off-by: Jonathan Corbet <corbet@lwn.net>