count(unit = "milliseconds", opts) {
    if (!this.isValid) return NaN;
    const start = this.start.startOf(unit, opts);
    let end;
    if (opts?.useLocaleWeeks) {
      end = this.end.reconfigure({ locale: start.locale });
    } else {
      end = this.end;
    }
    end = end.startOf(unit, opts);
    return Math.floor(end.diff(start, unit).get(unit)) + (end.valueOf() !== this.end.valueOf());
  }
Returns the count of minutes, hours, days, months, or years included in the Interval, even in part.
Unlike {@link Interval#length} this counts sections of the calendar, not periods of time, e.g. specifying 'day'
asks 'what dates are included in this interval?', not 'how many days long is this interval?'
@param {string} [unit='milliseconds'] - the unit of time to count.
@param {Object} opts - options
@param {boolean} [opts.useLocaleWeeks=false] - If true, use weeks based on the locale, i.e. use the locale-dependent start of the week; this operation will always use the locale of the start DateTime
@return {number}