Add customer note to all admin emails

functions.php

<?php 

add_action( 'woocommerce_email_after_order_table', 'studiowp_woocommerce_email_after_order_table_customer_note', 10, 4 );
function studiowp_woocommerce_email_after_order_table_customer_note( $order, $sent_to_admin, $plain_text, $email ) {
    if ( $sent_to_admin ) {
	    if ( $order->get_customer_note() != '' ) {
		    echo sprintf( '<h2>%s</h2>', __( 'Customer note', 'woocommerce' ) );
		    echo sprintf( '<p><strong>%s</strong></p>', $order->get_customer_note() );
	    }
    }
}