Add new maintainers for the project

As per the trustedfirmware.org Project Maintenance Process [1], the
current maintainers of the TF-A project have nominated some contributors
to become maintainers themselves. List them in the maintainers.rst file
to make this official.

[1] https://developer.trustedfirmware.org/w/collaboration/project-maintenance-process/

Change-Id: Id4e3cfd12a9074f4e255087fa5dd6fa5f902845f
Signed-off-by: Sandrine Bailleux <sandrine.bailleux@arm.com>

docs/about/maintainers.rst

@@ -33,6 +33,16 @@ Maintainers
 :G: `bipinravi-arm`_
 :M: Joanna Farley <joanna.farley@arm.com>
 :G: `joannafarley-arm`_
+:M: Julius Werner <jwerner@chromium.org>
+:G: `jwerner-chromium`_
+:M: Varun Wadekar <vwadekar@nvidia.com>
+:G: `vwadekar`_
+:M: Andre Przywara <andre.przywara@arm.com>
+:G: `Andre-ARM`_
+:M: Lauren Wehrmeister <Lauren.Wehrmeister@arm.com>
+:G: `laurenw-arm`_
+:M: Madhukar Pappireddy <Madhukar.Pappireddy@arm.com>
+:G: `madhukar-Arm`_
 
 
 .. _code owners: