Implement a function useFocus() that allows focusing on an HTML element programmatically.

The function should:

• Return an object containing a ref property to attach to an element.
• Return a focus() method that focuses the attached element when called.
• Ensure calling focus() on an unmounted element does not throw an error.

Examples

const { ref, focus } = useFocus();
const input = document.createElement('input');
ref.current = input;
focus();
console.log(document.activeElement === input); // true