Added default language pack (en-gb)

catalog/mail/transaction.php

@@ -0,0 +1,6 @@
+<?php
+// Text
+$_['text_subject']  = '%s - Affiliate Commission';
+$_['text_received'] = 'Congratulations! You have received a commission payment from the %s affiliate program';
+$_['text_amount']   = 'You have received:';
+$_['text_total']    = 'Your total amount of commission is now:';