This implements more functionality of the existing tool and, as
'reload' is an unreliable feature that doesn't work more often
than not, the last bit that we will replicate.
The command follows the original for the most part, with the most
important difference being the installed template, which doesn't
provide any sample functionality and uses modern JS syntax.
https://gitlab.gnome.org/GNOME/gnome-shell/issues/1234
This replicates the most basic functionality of the existing
gnome-shell-extension-tool, albeit using a git/gio/gsettings
style command interface rather than plain options; this will
allow us to implement more complex commands that have options
on their own in the future.
https://gitlab.gnome.org/GNOME/gnome-shell/issues/1234
