README: Add maintainers section

Julien has kindly offered to help maintain kvmtool, but it occurred to
me that we don't actually provide any maintainer contact details in the
repository as it stands.

Add a brief "Maintainers" section to the README, immediately after the
"Contributing" section so that people know who to nag about merging and
reviewing patches.

Acked-by: Marc Zyngier <marc.zyngier@arm.com>
Acked-by: Julien Thierry <julien.thierry@arm.com>
Signed-off-by: Will Deacon <will@kernel.org>
diff --git a/README b/README
index 52124b8..591f84f 100644
--- a/README
+++ b/README
@@ -111,3 +111,9 @@
  git config format.subjectprefix "PATCH kvmtool"
 
 in the git repository.
+
+Maintainers
+-----------
+
+kvmtool is maintained by Will Deacon <will@kernel.org> and Julien Thierry
+<julien.thierry@arm.com>.