maintainer updates as per opencontainers#1101

Signed-off-by: H. Vetinari <h.vetinari@gmx.com>

MAINTAINERS

@@ -6,3 +6,6 @@ Tianon Gravi <admwiggin@gmail.com> (@tianon)
 Qiang Huang <h.huangqiang@huawei.com> (@hqhq)
 Aleksa Sarai <asarai@suse.de> (@cyphar)
 Giuseppe Scrivano <gscrivan@redhat.com> (@giuseppe)
+Akihiro Suda <akihiro.suda.cz@hco.ntt.co.jp> (@AkihiroSuda)
+Kir Kolyshkin <kolyshkin@gmail.com> (@kolyshkin)
+Sebastiaan van Stijn <github@gone.nl> (@thaJeztah)