New player event: PLAYER_EVENT_ON_PET_ADDED_TO_WORLD (#3)

Co-authored-by: UltraNix <ultranix@gmail.com>

Hooks.h

@@ -204,6 +204,7 @@ namespace Hooks
         // UNUSED                               =     40,       // (event, player)
         // UNUSED                               =     41,       // (event, player)
         PLAYER_EVENT_ON_COMMAND                 =     42,       // (event, player, command) - player is nil if command used from console. Can return false
+        PLAYER_EVENT_ON_PET_ADDED_TO_WORLD      =     43,       // (event, player, pet)
 
         PLAYER_EVENT_COUNT
     };