Bug 15140: Display $i when ind2==8

Bug 15140: Display $i when ind2==8

See MARC specification.
Note that we have a preceding text before all 776s too.

Test plan:
[1] Set field 776 ind2 to 8. And add text in $i.
[2] Look for this text on OPAC detail and staff detail.

Signed-off-by: Marcel de Rooy <m.de.rooy@rijksmuseum.nl>
Signed-off-by: Felix Hemme <felix.hemme@thulb.uni-jena.de>
Signed-off-by: Nick Clemens <nick@bywatersolutions.com>
Signed-off-by: Jonathan Druart <jonathan.druart@bugs.koha-community.org>