A searchable guide to the complete WordPress Icon Library (@wordpress/icons) package from Gutenberg.
import { Icon, plus } from '@wordpress/icons';
<Icon icon={plus} />
<svg xmlns="http://www.w3.org/2000/svg" viewBox="0 0 24 24" aria-hidden="true" focusable="false"><path d="M18 11.2h-5.2V6h-1.6v5.2H6v1.6h5.2V18h1.6v-5.2H18z"></path></svg>
plus – WordPress Icon Library