Add Austin Gillmann <alucard@cuntflaps.me> to the mailmap

I do intend to increase my commit count here as a contributor to pomf/pomf, so I will add myself to the git mailing map for that reason.

.mailmap

@@ -3,3 +3,4 @@ Eric Johansson <neku@pomf.se> nokonoko <petanull@gmail.com>
 Eliot Whalan <ewhal@pantsu.cat> <contact@pantsu.cat>
 Juuso Lapinlampi <wub@partyvan.eu>
 alchimist <alchimist@nwa.xyz> cenci0 <alchimist94@gmail.com>
+Austin Gillmann <alucard@cuntflaps.me>