[Feature] Extend `since` with `abbreviated`

[Nfinished]

This pr extends the return of the since method with a new string prop abbreviated following the pattern 1y2m3d4m5s. I've found myself doing it enough times that I think it's a worthy addition.

I realize that m for month and minute can be ambiguous, but I think most if not all of the time it should be contextually apparent.

abbreviated also deviates from the other properties in that it is always positive regardless of relativity, it's open to discussion but I think it makes sense in context.

I've extended all tests and ensured they pass, and updated the Since type. I didn't update the readme because it already only covers two of the existing returns types.

[Nfinished]

Not sure why builds are failing -- seems environmental?

[Nfinished]

Also an open question - spaces or no spaces? No spaces fits the theme better but it's slightly easier to remove spaces than add them.

[spencermountain]

oh hey, this is cool. Is this the same as this?

Your scheme, it's human-readable purposes right? Maybe we could do both. Don't worry about the tests, i've borked master. I'll merge this today, if you're happy with it, or have thoughts on the ISO standard. Thank you!

[Nfinished]

I didn't know that spec existed but it makes sense that it does. Yeah I guess this is some middle ground between spec and readability? If that middle ground is the goal (which I think it should be), maybe we do default to spaces? What do you think?

[Nfinished]

Honestly either way someone somewhere's going to be inconvenienced so I'm at a loss.

[spencermountain]

yep. i agree. I'll merge it and take a look. thank you! This is a great idea.

[spencermountain]

any thoughts on this?

export interface Since {
  diff: Diff
  rounded: string
  qualified: string
  precise: string
  abbreviated: string[]
  iso: string
  direction: 'past' | 'present' | 'future'
}

{   ...,
    precise: '10 hours, 59 minutes ago',
    abbreviated: ['10h', '59m', '10s'],
    iso: 'P0Y0M0DT10H59M10S',
    direction: 'past'
}

the iso format doesn't go negative either - so it's pretty similar to your scheme. Let me know what you think, shouldn't release this until after the holidays. cheers

[Nfinished]

ha love using an array, very elegant sidestep. Good call on adding directionality too, otherwise it'd have to be inferred from another value. lgtm 👍

[Nfinished]

Oh what does this mean for 'now'? Is abbreviated an empty array? Is it ['now']? I guess ISO is just all zeroes.

[jecraig]

I would go with ['0s']. That should keep it consistent in usage and it's still friendly enough for users.