missing "now" option documentation

[renatodeleao]

Hi!

I found out about now option at this issue flatpickr/flatpickr#1284, which allow us to correct "today" highlighting when we have, and quoting:

"an implementation where the calendar is localized in a different time-zone than the user's local settings"

docs URL: https://flatpickr.js.org/options/

Can try to make a PR for it if you're interested!
Cheers 👋