Bug 14004: Add OpacAdditionalStylesheet and opaclayoutstylesheet

Bug 14004: Add OpacAdditionalStylesheet and opaclayoutstylesheet

Signed-off-by: Owen Leonard <oleonard@myacpl.org>
Signed-off-by: Katrin Fischer <katrin.fischer.83@web.de>
Signed-off-by: Jonathan Druart <jonathan.druart@bugs.koha-community.org>
(cherry picked from commit c009eeafed32f0da9ef3c81e5b3e748745c9f900)
Signed-off-by: Fridolin Somers <fridolin.somers@biblibre.com>
(cherry picked from commit 404155fbffd3b7052f7eae04a2d5e62a14a84eee)

Signed-off-by: Andrew Fuerste-Henry <andrew@bywatersolutions.com>