Proposed Functions: isAveilut() and isFastDay()

[ethanpil]

In the spirit of the function isAssurBemlacha() I would much appreciate the two additional functions isAveilut() and isFastDay() added to the HebCal api to help with automations. Some use cases I have in mind:

• Autoplay A Capella music instead of regular music when isAveilut() returns True
• Do not send daily menus when isFastDay() returns True

I would expect isAveilut() to return True for Sefirat HaOmer days, Bein HaMeitzarim days, etc.
I would expect isFastDay() to return True for 17 Tammuz, 9 Av, Yom Kippur, Tzom Gedalia, etc

Any thoughts on this proposal?

[mjradwin]

If you'd like to implement these, we would be happy to receive a pull request.

You can implement isFastDay() using something like this

import {getHolidaysOnDate, flags} from '@hebcal/core';

const today = new Date();
const events = getHolidaysOnDate(today, false) || [];
const fastDay = events.find((ev) => ev.getFlags() & (flags.MAJOR_FAST | flags.MINOR_FAST));