mailmap: mask accentless variant for Công Danh

Signed-off-by: Junio C Hamano <gitster@pobox.com>

.mailmap

@@ -60,6 +60,7 @@ David Turner <novalis@novalis.org> <dturner@twopensource.com>
 David Turner <novalis@novalis.org> <dturner@twosigma.com>
 Derrick Stolee <dstolee@microsoft.com> <stolee@gmail.com>
 Deskin Miller <deskinm@umich.edu>
+Đoàn Trần Công Danh <congdanhqx@gmail.com> Doan Tran Cong Danh
 Dirk Süsserott <newsletter@dirk.my1.cc>
 Eric Blake <eblake@redhat.com> <ebb9@byu.net>
 Eric Hanchrow <eric.hanchrow@gmail.com> <offby1@blarg.net>