Add oslo.i18n to list of developer documentation
Add oslo.i18n to list of developer documentation

Change-Id: I97c87b77105f8e0057be8d0bb17ce53e6b9023f6

openstack/openstack-manuals,saeki-masaki/openstack-manuals,saeki-masaki/openstack-manuals,openstack/openstack-manuals,potsmaster/openstack-manuals,potsmaster/openstack-manuals,Akasurde/openstack-manuals,kairoaraujo/openstack-manuals,openstack/openstack-manuals,AlekhyaMallina-Vedams/openstack-manuals,AlekhyaMallina-Vedams/openstack-manuals,openstack/openstack-manuals,gongysh2004/openstack-manual,kairoaraujo/openstack-manuals,AlekhyaMallina-Vedams/openstack-manuals,gongysh2004/openstack-manual,Akasurde/openstack-manuals