added more route instructions

routes/signed.php

@@ -1,6 +1,11 @@
 <?php
 
-// 'signed' middleware applied via App\Providers\Route
+/**
+ * 'signed' middleware and prefix applied to all routes
+ *
+ * @see \App\Providers\Route::mapSignedRoutes
+ * @see \modules\OfflinePayments\Routes\signed.php for module example
+ */
 
 Route::get('invoices/{invoice}', 'Portal\Invoices@signed')->name('signed.invoices.show');
 Route::get('invoices/{invoice}/print', 'Portal\Invoices@printInvoice')->name('signed.invoices.print');