mailmap: add entry for myself

Signed-off-by: Tong Wu <wutong1208@outlook.com>
Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>

.mailmap

@@ -24,3 +24,5 @@ rcombs <rcombs@rcombs.me> <rodger.combs@gmail.com>
 <lq@chinaffmpeg.org> <liuqi05@kuaishou.com>
 <ruiling.song83@gmail.com> <ruiling.song@intel.com>
 Cosmin Stejerean <cosmin@cosmin.at> Cosmin Stejerean via ffmpeg-devel <ffmpeg-devel@ffmpeg.org>
+<wutong1208@outlook.com> <tong1.wu-at-intel.com@ffmpeg.org>
+<wutong1208@outlook.com> <tong1.wu@intel.com>