WIP Continous published guides: Mention lifetime
WIP Continous published guides: Mention lifetime

Explain which OpenStack releases are covered by a guide.

Change-Id: I2520836eb55a0b222decc9092ce4828b9482f1e5

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