Returns a field to access the week of month based on this

`WeekFields`

.

This represents the concept of the count of weeks within the month where weeks start on a fixed day-of-week, such as Monday. This field is typically used with `dayOfWeek()`

.

Week one (1) is the week starting on the `getFirstDayOfWeek()`

where there are at least `getMinimalDaysInFirstWeek()`

days in the month. Thus, week one may start up to `minDays`

days before the start of the month. If the first week starts after the start of the month then the period before is week zero (0).

For example:

- if the 1st day of the month is a Monday, week one starts on the 1st and there is no week zero

- if the 2nd day of the month is a Monday, week one starts on the 2nd and the 1st is in week zero

- if the 4th day of the month is a Monday, week one starts on the 4th and the 1st to 3rd is in week zero

- if the 5th day of the month is a Monday, week two starts on the 5th and the 1st to 4th is in week one

This field can be used with any calendar system.

In the resolving phase of parsing, a date can be created from a year, week-of-month, month-of-year and day-of-week.

In strict mode , all four fields are validated against their range of valid values. The week-of-month field is validated to ensure that the resulting month is the month requested.

In smart mode , all four fields are validated against their range of valid values. The week-of-month field is validated from 0 to 6, meaning that the resulting date can be in a different month to that specified.

In lenient mode , the year and day-of-week are validated against the range of valid values. The resulting date is calculated equivalent to the following four stage approach. First, create a date on the first day of the first week of January in the requested year. Then take the month-of-year, subtract one, and add the amount in months to the date. Then take the week-of-month, subtract one, and add the amount in weeks to the date. Finally, adjust to the correct day-of-week within the localized week.