Enable passing formatStyle to Intl.DateTimeFormat

[erlandsona]

Here A style argument is being passed to the config of the Intl.RelativeTimeFormat constructor.

But Here There's no way to configure the timeStyle or dateStyle properties as described in the MDN docs below:

https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Intl/DateTimeFormat/DateTimeFormat#using_timestyle_and_datestyle

We have a use case where for DateTime's fitting within the users "today" we only want to display the timeStyle: 'short', but for DateTimes after today we only want to display the dateStyle: 'short' and with the current api I'm not sure how exactly to go about that 🤔

[keithamus]

A PR adding attributes+props for timeStyle/dateStyle would be welcome.