use modern import/subclass style for signals

[wbolster]

follow-up to #68

[wbolster]

this was missing from #68, and flagged during review after uploading to extensions.gnome.org // cc @axxapy

[axxapy]

Nice to know! I actually was looking into it since there was nothing in the documentation (or I missed it), I checked gnome's own source code and noticed they still use old way for signals together with new imports, so I decided it's okay:

• https://gitlab.gnome.org/GNOME/gnome-shell/-/blob/main/js/dbusServices/dbusService.js#L6
• https://gitlab.gnome.org/GNOME/gnome-shell/-/blob/main/js/misc/signals.js#L3

Now, when I know the proper solution, I can see other places where they use the new way:

Should've done deeper investigation. Thanks for addressing it!

[wbolster]

no worries, it was a quick fix and the reviewer pointed me in the right direction.

your PR was fantastic and would've cost me ages to do myself, since i am not hands-on at all (anymore) in the gnome ecosystem.