Add date ranges and support RRULEs

This code adds two features:

Adding support for date range queries; works like this:

(async () => {
  const list = await dav.listEvents(
    SimpleCalDAV.simplifyEvent,
    {
      start: new Date("2022-12-20T00:00:00"),
      end: new Date("2022-12-30T00:00:00")
    }
  )

Adding support for recurring events (RRULE entries), using the rrule library. To be honest, the code is a bit messy at this point; but I think the whole library would need a refactoring anyway. Also I need to mention that the code assumes that the result of the transform callback is an object with start and end properties, which might not be desireable.

So, please feel free to use this code as you see fit.

By the way, I very much appreciate your previous work, especially that you have implemented it with explicit support for Radicale!

TimDaub / simple-caldav

Add date ranges and support RRULEs #43