Now we have more documents for plugins on stable release,
support and their testing policy. Let's prepare a
index page for it will be easy for plugins maintainer.
Also renaming the stable support policy section to have a clear
Adding redirect links for moved documents.
This commit adds an .htaccess file to the tempest docs to handle
redirecting old paths to the new location. Before the docs migration in
the past we had docs located at docs.openstack.org/developer/tempest and
now things are located in docs.openstack.org/tempest/latest. With this
file we should be properly redirecting old links to the new location.