I want to be able to use a custom template to display the time the alert started to fire and how much time is it firing for, something like:

⌛ Firing since: 2024-02-12 18:15:38.457 +0000 UTC (for 3 hours 42 minutes 21 seconds).

We already have .StartsAt field for alert, but there's no template helper to 1) use time.Since(), and 2) pretty-format duration, so it would be lovely to have it here as well.