Added default language pack (en-gb)

catalog/extension/advertise/google.php

@@ -0,0 +1,6 @@
+<?php
+
+// Text
+$_['text_cron_email_message'] = '<p>This is an automated report of the latest CRON task performed by your Google Shopping extension.</p><p>%s</p>';
+$_['text_cron_email_subject'] = 'CRON job report - Google Shopping on OpenCart';
+$_['text_per_day']            = '$%s / day';