Clarify timestamp use and need for abbreviations
src/notifications/timestamp-label.c
has timestamp suffixes for units of time from a second to a year. We aren’t given much more information apart from that. Some of these units may not have common abbreviations in some languages, e.g. there is no abbreviation for month in French. I can’t use "m" because that’s minutes. "mo" doesn’t feel natural and I don’t expect readers to understand what it means. Can I just put the whole "mois" word? I’m not given any clue as to what the constraints are or even why it should be an abbreviation.
FWIW month is the only problematic one in French, but other ones may be a problem in other languages as well.