Register "details" meta field on WooCommerce product_cat terms

functions.php

<?php

add_action( 'init', 'wpm_product_cat_register_meta' );
/**
 * Register details product_cat meta.
 *
 * Register the details metabox for WooCommerce product categories.
 *
 */
function wpm_product_cat_register_meta() {

	register_meta( 'term', 'details', 'wpm_sanitize_details' );

}

/**
 * Sanitize the details custom meta field.
 *
 * @param  string $details The existing details field.
 * @return string          The sanitized details field
 */
function wpm_sanitize_details( $details ) {

	return wp_kses_post( $details );

}