title: Custom Order received return URL query args in Woocommerce
body: <p>Wehenever I place an order using Woocommerce I get an URL with a few parameters. It looks like this -> <code>/order-received/12240/?key=wc_order_5bf66c9ea4f0a</code></p>
  
  <p>I would like to add a few of my own to this URL. But i cant find where this URL is generated.</p>
  
  <p>What i tried:</p>
  
  <p>to add  <code>add_query_arg( 'foo', 'bar' )</code> to the thank-you.php file. Didnt work. </p>
  
  <p>Also tried :</p>
  
  <pre><code>add_action('woocommerce_checkout_order_processed','my_function');
  function my_function() {
       add_query_arg( 'foo', 'bar' );
  }
  </code></pre>