enqueue polyfill.io

// Register Script
function abe_polyfills() {

	wp_register_script( 'polyfill-io', 'https://cdn.polyfill.io/v2/polyfill.min.js', false, false, false );
	wp_enqueue_script( 'polyfill-io' );

}
add_action( 'wp_enqueue_scripts', 'abe_polyfills' );