A searchable guide to the complete WordPress Icon Library (@wordpress/icons) package from Gutenberg.
import { Icon, square } from '@wordpress/icons';
<Icon icon={square} />
<svg xmlns="http://www.w3.org/2000/svg" viewBox="0 0 24 24" aria-hidden="true" focusable="false"><path fill="none" d="M5.75 12.75V18.25H11.25M12.75 5.75H18.25V11.25" stroke="currentColor" stroke-width="1.5" stroke-linecap="square"></path></svg>
square – WordPress Icon Library