Use alarm-clock-elapsed sound instead of complete
Currently when creating a timer when it's done it will play the "complete" sound: https://gitlab.gnome.org/GNOME/gnome-clocks/-/blob/master/src/timer.vala#L426
I think according to the freedesktop sound naming specification (http://0pointer.de/public/sound-naming-spec.html#alerts) however that alarm-clock-elapsed would be a better sound to play. In most sound themes I looked at right now, alarm-clock-elapsed was a much longer sound than complete and should help actually hearing the alarm. Currently in the sound theme I use the complete sound is just a second but the alarm clock elapsed sound is multiple seconds so I would definitely hear it.
I think at least offering a setting to use alarm-clock-elapsed (or maybe any sound files) would be useful for people with quiet/short/no sounds for the complete sound. (see also: #60 (closed), but I would definitely want to keep my system sounds because I like the customization with them much more)