Add contributors.txt file
Add contributors.txt file

Signed-off-by: Acans <13981823f2f9efe902e50c4b770ae153c998f83d@simplemachines.org>

margarett/SMF2.1,MustafaCan/SMF2.1,StealthWombat/SMF2.1-more-forkery,StealthWombat/SMF2.1-more-forkery,georaldc/SMF2.1,mkress/SMF2.1,margarett/SMF2.1,georaldc/SMF2.1,mkress/SMF2.1,mkress/SMF2.1,MustafaCan/SMF2.1