weekStartDay is not working with typescript

[martinagrbic]

Implementation of weekStartDay property is reporting following error when it is used:

Argument of type '{ language: string; input: { element: HTMLElement; format: string; }; date: Date; showAlways: false; weekStartDay: string; }' is not assignable to parameter of type 'DatePickerOptions'.
Object literal may only specify known properties, and 'weekStartDay' does not exist in type 'DatePickerOptions'.ts(2345)