trans_languages
Return a list of all languages present in the given translated text (#trans{} record).
If not translation is given, then the empty list is returned.
Example usage:
{% for iso in text|trans_languages %} {{ iso }} {% endfor %}
If the text has the value:
#trans{ tr = [{en, <<>>}, {nl,<<"Hallo">>}] }
Then this will show en nl.