doc: Add index into the sidebar.
doc: Add index into the sidebar.

Signed-off-by: Tommi Virtanen <9ab2264cc7e4806727ef3fc8f99e05b759bbf6e0@dreamhost.com>

ajnelson/ceph,ajnelson/ceph,ajnelson/ceph,ajnelson/ceph,ajnelson/ceph,ajnelson/ceph