Fix Storybook after webpack 5 upgrade (https://github.com/woocommerce/woocommerce-blocks/pull/11456)

plugins/woocommerce-blocks/storybook/main.js

@@ -30,6 +30,7 @@ module.exports = {
 			include: /node_modules/,
 			type: 'javascript/auto',
 		} );
+		config.externals = [ 'react-dom/client' ];
 		return config;
 	},
 };