only webp with performance plugin

only-webp.php

<?php
/**
 * Output only WebP sub size images.
 *
 * @wordpress-plugin
 * Plugin Name: WebP-only.
 * Description:  Output only WebP sub size images.
 * Plugin URI:
 * Version:     1.0.0
 * Author:      Adam Silverstein, Google
 * License:     Apache License 2.0
 * License URI: https://www.apache.org/licenses/LICENSE-2.0
 */
 
function filter_webp_uploads_upload_image_mime_transforms( $mime_types ){
	$mime_types[ 'image/jpeg' ] = array( 'image/webp' ); // only output WebP for uploaded jpegs.

	return $mime_types;
}
add_filter( 'webp_uploads_upload_image_mime_transforms', 'filter_webp_uploads_upload_image_mime_transforms' );