add description to custom autoloader for git submodules

Author: joonlabs

src/autoloader.php

@@ -1,9 +1,13 @@
 <?php
 /**
- * Automatically loads all required und used classes.
+ * php-graphql features an own autoloader, for cases where this library is not
+ * used and included via composer, but rather as a git submodule. If you are using
+ * composer for managing libraries, etc. you can ignore this file and use the default
+ * composer autoloader via `require '/vendor/autoload.php'`. However if you prefer using this
+ * project via git submodules, you can use this autoloader via `require /php-graphql/src/autoloader.php`.
  */
 spl_autoload_register(function ($className) {
-    // replace remove GraphQL namespace
+    // remove GraphQL namespace
     $className = str_replace("GraphQL\\", "", $className);
 
     // change \ to /