[ Thanks to An Anonymous Reader for this link. ]
“The extensions will be created by the users (so these
will be unofficial extensions), but they will have to go through a
review process and once approved, they will be hosted on
http://extensions.gnome3.org (website not functional yet) and
you’ll be able to install them with a click as well as
enable/disable them without having to restart GNOME Shell, like
Chrome or Firefox extensions.