Nominate Gari Singh to be a maintainer for fabric

I'd like to nominate Gari Singh to become a maintainer for the fabric
project. Gari has really stepped up his level of contribution and
reviews over the past few weeks. His reviews are always thoughtful
and constructive. He has also been very active on Slack, helping
newcomers with their questions about how things work, and are
put together.

Gari, for those that do not know, is CTO for the IBM blockchain
development team, so he definitely has a vested interest in
helping us create an awesome open source foundation.

Change-Id: If888565389ac440815a00ca3fdd564bc51df0f17
Signed-off-by: Christopher Ferris <chrisfer@us.ibm.com>

docs/MAINTAINERS.md

@@ -12,3 +12,4 @@
 | Simon Schubert | corecode || sis@zurich.ibm.com
 | Chris Ferris | christo4ferris | ChristopherFerris | chrisfer@us.ibm.com
 | Srinivasan Muralidharan | muralisrini | muralisr | muralisr@us.ibm.com
+| Gari Singh | mastersingh24 | mastersingh24 | gari.r.singh@gmail.com