feat: use moment.js for timeAgo

[akloeckner]

also export the moment class to user space
this will enable the user to do

moment.locale('de');

in their config.js.

[rchl]

This adds quite a chunk of data to the bundle (maybe 500kb or so) but I guess it's probably fine.

[akloeckner]

I tried to find a way to avoid bundling all the locales. We could only bundle "popular" locales like ru, de, en, pl. Or provide info on how the user can load locales. Both don't seem very appealing to me...

[akloeckner]

Actually, timeAgo seems to be used only for the default tooltip in history tiles and the corresponding example. Maybe it's better to not touch that function or remove it altogether...

[akloeckner]

So, this is a simple one now... I'll PR i18n separately...

[rchl]

I've briefly looked at using date-fns instead, which is preferred in the community now (even https://momentjs.com/ discourages its use), but date-fns doesn't currently support setting locale globally so it wouldn't be as flexible. We would need to import all languages we want to support up-front (that seems fine) and then all uses of date-fns functions would basically have to be wrapped in a function that uses the chosen locale (which user could define in the config).

I'll wait to hear what you have to say about that before merging this one.

(We would still have to include moment.js for the chart.js library)

[akloeckner]

I think, it's good to stick with moment.js until we sort this out once and for all. Since chart.js uses moments we might even end up deciding to stick with it despite its deprecation.

Wrapping in a function wouldn't really stop me from using it, though. Currently timeAgo is the only direct usage of that sort. And it's a wrapper already. (Maybe the functional programming variants would make good wrappers, btw.)

[rchl]

BTW. If we advertise the use of something like moment.locale('de'), we should rather introduce a config option for it so that we can abstract locale change and potentially replace the underlying implementation in the future.