add a external link icon to viaf links, correct bug #27355 (https://mantis.culture.fr/mantis/view.php?id=27355)
<?php
namespace CorpusParole\Services;
use CorpusParole\Models\Document;
interface TranscriptManagerInterface {
function getConverter($converterKey, Document $document, $source);
function getConverterUrl($converterKey, Document $document, $url);
}