In the Grommet FormField documentation, it states under Component;
The component may be custom as long it supports the properties of name, value, onChange (event => {}), while event has either event.value or event.target.value.
I'd like to implement a custom component but don't understand how it needs to interact with a controlled Form component to supply its value property. Is there an example somewhere that shows how to implement a custom component in a FormField?