Support 'FOLK' as corpus sigle for DGD associated corpora

Change-Id: I2b35d6449c90c5d497ef91f2ab1f7af5fc222cde
diff --git a/lib/KorAP/XML/Meta/I5.pm b/lib/KorAP/XML/Meta/I5.pm
index c82fef8..e887279 100644
--- a/lib/KorAP/XML/Meta/I5.pm
+++ b/lib/KorAP/XML/Meta/I5.pm
@@ -377,7 +377,7 @@
     };
 
     # DGD treatment
-    if ($self->{T_title} && !$self->{A_externalLink} && $self->{_corpus_sigle} eq 'AGD') {
+    if ($self->{T_title} && !$self->{A_externalLink} && $self->{_corpus_sigle} =~ /^(?:[AD]GD|FOLK)$/) {
       my $transcript = $self->{T_title};
       $transcript =~ s/_DF_\d+$//i;
       $self->{A_externalLink} = $KORAP_LINK_PREF . 'title=DGD,' .