[igx-date-picker] required attribute is always set to false

[jamesuhl]

Is your feature request related to a problem? Please describe.

Setting the date picker component to “required” does not set aria-required attribute

Describe the solution you'd like

When setting the Validators.required in the Angular constructor, the aria-required attribute should change to "true"

Alternatives

The HTML5 “required” attribute is considered a better way to designate required form elements, unless backwards compatibility to HTML4 or XHTML is a concern.