feat(FormField): pass required to the control

[levithomason]

Fixes #911

This PR updates the FormField to pass the required prop to the control component.

<Form.Field control='input' required />
//=> has child: <input required>

<Form.Input required />
//=> has child: <Input required />
//=> has child: <input required />

[levithomason]

Released in semantic-ui-react@0.61.3.

[su6838354]

when the component is select/dropdown, it may not effective.

[levithomason]

Correct, there is no required prop for a Dropdown (nor Select). There is no DOM node for the browser to "require" a value from. The Dropdown is constructed from HTML and CSS.

You should instead use form validation, #407.