Add luna.archlinux.org

This is currently only covered by playbooks/all-hosts-basic.yml

Signed-off-by: Florian Pritz <bluewind@xinu.at>

hosts

@@ -9,3 +9,6 @@ apollo.archlinux.org
 
 [soyuz]
 soyuz.archlinux.org
+
+[luna]
+luna.archlinux.org