top-notch timer/alarm addon.

I've been testing a few different alarm addons, so in case anyone's interested in what it can and can't do, here's what I have from my own testing notes:

Also the "CONS" aren't so much me trying to be critical or saying the addon needs something, more me trying to note what is or is not there for the benefit of other users looking for in-depth detail prior to installing. If I personally decide I need those features, you'll likely see a github ticket + PR.

PROS:

- Open-source under MPL 2 license with a public code repository (linked to directly via homepage link; direct link is https://github.com/Nudin/timer-webext). Also explicitly credits the fork it was based on (excellent job to both authors!)
- No permissions required
- Can add labels when creating new alarms or countdown timers and re-use.
- Easy to create / edit / delete / toggle on or off
- Able to have multiple alarms at once. I created 25 alarms without running into any hard-limits. This only applies to alarms (e.g. Stopwatch and Countdown Timers *do* have limits)
- Able to define Alarm as one-time (default) or have it repeat weekly on one or more specific days of the week (Sun-Sat).
- Has sounds and clicking on a sound button during setup plays preview.
- Alarms can be setup to have a Snooze option or not
- Can choose from Snooze Presets of 5, 10, 20, 30, or 60 minutes.
- Stopwatch has Start -> Stop / Lap -> Resume / Reset

CONS:

- On Firefox Addons page, addon is listed as "Timer" instead of as "LibreTimer". Probably leftover from original project being named "Timer" but might confuse people if they installed multiple timer addons (e.g. for testing).
- For stopwatch, you only get 1 stopwatch counter.
- For countdown timer, you run into a hard-limit of 4 countdown timers.
- Does not allow you to define count-down timers less than 1 minute.
- I love 24-hr time format but if you prefer 12-hr, there's no option for that.
- No Addon Preferences, no Options section.
- No way to export created alarms / settings to local backup file (e.g. json / xml / etc) for easy migrations between machines.
- No way to set volume of alarms independent of system / browser sound levels.
- No way to set custom alarms (e.g. play custom sound file / youtube vid / etc)
- Snooze Interval only allows choosing from specific presets.
- Snooze Interval Presets must be selected when the alarm is created and cannot be selected at the time alarm goes off.

Tested on 2024-04-28 / FF 124.0.1 / addon v0.1.2 (aka May 16, 2020 upload) / Fedora Linux w Cinnamon desktop