Notify: fix send email notification language binding

[chessbr]

When user place an order, the language for the order is the one collected from the browser language and it can vary from en, en-gb, en-au and others. This can cause issues when the language is not configured correctly of each notification.

Maybe a good solution is to select many languages to be used in a single template or maybe make the language code fallback to main locale, e.g. if the language is en-gb and there is no template for that, fallback to en. The same could happen for other languages like pt-br and pt-pt fallback to pt.