Adding locale.duration

[gfwilliams]

We have stuff for absolute time, distance, temperature, but I think it also makes sense to have a nicely formatted duration. For example in the stopwatch, or other apps...

• <2 minutes => 23 sec
• <60 minutes => 1 min 23
• 1 hr 23

something like that?

[MaBecker]

maybe also have

• > 24 h => 1 d 2 hr 23

[srl295]

It would be best to make this a polyfill of the actual ecma402 functions, tc39/ecma402#47

Actually, I'll make an issue about that general topic and see what I can do.