mailmap: Add a line for Pierre-Antoine.

* .mailmap: Add entry for Pierre-Antoine.

.mailmap

@@ -56,6 +56,7 @@ Nils Gillmann <ng0@n0.is> <ngillmann@runbox.com>
 Nils Gillmann <ng0@n0.is> <niasterisk@grrlz.net>
 Nils Gillmann <ng0@n0.is> <ng@niasterisk.space>
 Nils Gillmann <ng0@n0.is> <ng0@libertad.pw>
+Pierre-Antoine Rouby <pierre-antoine.rouby@inria.fr>
 Pjotr Prins <pjotr.guix@thebird.nl> <pjotr.public01@thebird.nl>
 Pjotr Prins <pjotr.guix@thebird.nl> <pjotr.public12@thebird.nl>
 Pjotr Prins <pjotr.guix@thebird.nl> <pjotr.public12@email>