KendoReact DatePicker custom calendar no focus on open

Hi Andrei,

There is an internal property which we're passing for most custom KendoReact components in order to obtain their `ref` and make focusing possible.

I've just noticed that in our documentation we're no spreading the properties we receive for the custom calendar, which leaves out the above mentioned internal property. The correct syntax is:

const CustomCalendar = (props) => {
  return (
    <MultiViewCalendar
      {...props}
      views={1}
    />
  );
};

I've modified the demo in stackblitz to correctly customize the Calendar, in order for the autofocus to work. Please find it bellow:
https://stackblitz.com/edit/react-smkcjx?file=app/customCalendar.jsx

I do apologize for any inconvenience this might have caused and we will be quick to update it in our docs.

Regards,
Kiril
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