Website URL incorrect

Hi, I came across a Bug where the plugin path is build incorrectly. I am running a website on a Subdomain in a Subfolder and the following strips out the subfolder in the URL:

// woocommerce-email-test/functions.php
function show_test_email_buttons(){

	global $test_email_class;

	foreach( $test_email_class as $class=>$name ) {

		echo " <a href='/?woocommerce_email_test={$class}' class='button button-primary' target='_blank'>{$name}</a> ";			

	}
}

The correct way should be the following:

// woocommerce-email-test/functions.php
function show_test_email_buttons(){

	global $test_email_class;

	foreach( $test_email_class as $class=>$name ) {

		echo " <a href='" . get_site_url() . "?woocommerce_email_test={$class}' class='button button-primary' target='_blank'>{$name}</a> ";

	}
}

https://ww.wp.xz.cn/plugins/woocommerce-email-test/