read unix epoch timestamps with date widget.

[harshil1507]

Is your feature request related to a problem? Please describe.
Need a way to read unix timestamps when the field is of date type.

Describe the solution you'd like
A flag isEpoch or a function to override how date values are converted, readValue: () => (...)

Describe alternatives you've considered
Tried overriding the widget using custom factory where DateTimeSelect is a simple wrapper for Antd date picker which converts epoch to human readable time format.

factory: (props) => {
      return <DateTimeSelect {...props} />;
    },

Additional context
I keep on getting this error: "Can't convert value 1733202000 as Date"

With the custom widget(factory) applied, I get the value as undefined