Bug 26394: Update .mailmap

Bug 26394: Update .mailmap

The .mailmap file used to generate the stats is different from the one we have in our repo. It's much more complete and should be integrated into Koha.

Test plan:
Confirm that the different mappings are correct

Signed-off-by: Martin Renvoize <martin.renvoize@ptfs-europe.com>
Signed-off-by: Marcel de Rooy <m.de.rooy@rijksmuseum.nl>
Signed-off-by: Jonathan Druart <jonathan.druart@bugs.koha-community.org>
(cherry picked from commit 51fd1db1cf8ee39d74be436d4bab83955a3c8a18)
Signed-off-by: Victor Grousset/tuxayo <victor@tuxayo.net>