Support for unimplemented options allowed in `RRULE`#11

- Taken from: https://github.com/jakubroztocil/rrule#rrule-constructor --- | Complete | Option | Description | |---------------------------------------------------------------------------------------------------|-----------------|---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------| | ✔ | `BYMONTH` | If given, it must be either an integer, or a sequence of integers, meaning the months to apply the recurrence to. | | ✔ | `BYMONTHDAY` | If given, it must be either an integer, or a sequence of integers, meaning the month days to apply the recurrence to. | | ✔ (1770648) | `WKST` | The week start day. Must be one of the `RRule.MO`, `RRule.TU`, `RRule.WE` constants, or an integer, specifying the first day of the week. This will affect recurrences based on weekly periods. The default week start is `RRule.MO`. | | ✔ (4d4fbd1, #271) | `BYSETPOS` | If given, it must be either an integer, or a sequence of integers, positive or negative. Each given integer will specify an occurrence number, corresponding to the nth occurrence of the rule inside the frequency period. For example, a `BYSETPOS` of `-1` if combined with a RRule.MONTHLY frequency, and a `BYWEEKDAY` of (`RRule.MO`, `RRule.TU`, `RRule.WE`, `RRule.TH`, `RRule.FR`), will result in the last work day of every month. | | ✔ (#271) | `BYYEARDAY` | If given, it must be either an integer, or a sequence of integers, meaning the year days to apply the recurrence to. | | ✔ (#271) | `BYWEEKNO` | If given, it must be either an integer, or a sequence of integers, meaning the week numbers to apply the recurrence to. Week numbers have the meaning described in ISO8601, that is, the first week of the year is that containing at least four days of the new year. | | ✘ | `BYHOUR` | If given, it must be either an integer, or a sequence of integers, meaning the hours to apply the recurrence to. | | ✘ | `BYMINUTE` | If given, it must be either an integer, or a sequence of integers, meaning the minutes to apply the recurrence to. | | ✘ | `BYSECOND` | If given, it must be either an integer, or a sequence of integers, meaning the seconds to apply the recurrence to. | [Not part of RFC5545 spec](https://github.com/u01jmg3/ics-parser/pull/271#issuecomment-720176331) | ~~`BYWEEKDAY`~~ | If given, it must be either an integer (`RRule.MO === 0`), a sequence of integers, one of the weekday constants (`RRule.MO`, `RRule.TU`, etc.), or a sequence of these constants. When given, these variables will define the weekdays where the recurrence will be applied. It's also possible to use an argument n for the weekday instances, which will mean the nth occurrence of this weekday in the period. For example, with `RRule.MONTHLY`, or with `RRule.YEARLY` and `BYMONTH`, using `RRule.FR.nth(+1)` or `RRule.FR.nth(-1)` in `BYWEEKDAY` will specify the first or last Friday of the month where the recurrence happens. Notice that the RFC documentation, this is specified as `BYDAY`, but was renamed to avoid the ambiguity of that argument. | |