Bug 36463: Compress application/json

Bug 36463: Compress application/json

This patch simply adds application/json to the mod_deflate configuration

To test:
1 - Open the netowrk tab in firefox
2 - Load http://localhost:8081/api/v1/libraries
3 - Not the transferred size, and note no 'Content-Encoding: gzip" header
4 - Apply patch, reset_all (or edit /etc/koha/apache-shared.conf)
5 - Reload
6 - Note smaller size, note gzip header

Signed-off-by: Phil Ringnalda <phil@chetcolibrary.org>
Signed-off-by: Martin Renvoize <martin.renvoize@ptfs-europe.com>
Signed-off-by: Katrin Fischer <katrin.fischer@bsz-bw.de>