UTC-based week math

[dy]

Sometimes we may want to display week range as Sunday === 0 and Saturday === 6, so that the week starts from Sunday.
Now Dates.week.floor(date) gives end of Sunday, but would be nice to provide locale-dependent shift for the date.

[dy]

@calvinfo any thoughts on this?

[calvinfo]

Hey @dy thanks for reaching out. Unfortunately, I don't think any of us are focused directly on this library these days. I'm happy to add new contributors/owners, so long as you include new versions of the API, and follow semver for breaking changes.

[dy]

Sure, I'll come up with PR. I have these methods implemented