function
Retrieves the first day of the week for the given locale.
getLocaleFirstDayOfWeek(locale: string): WeekDay  locale  |  string |    A locale code for the locale format rules to use.  |  
WeekDay: A day index number, using the 0-based week-day index for en-US (Sunday = 0, Monday = 1, ...). For example, for fr-FR, returns 1 to indicate that the first day is Monday.
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Licensed under the Creative Commons Attribution License 4.0.
    https://angular.io/api/common/getLocaleFirstDayOfWeek