Add MicroKernelTrait advanced example run section

Author: dominikhajduk

configuration/micro_kernel_trait.rst

@@ -319,6 +319,17 @@ this:
     ├─ composer.json
     └─ composer.lock
 
+As before you can use PHP built-in server:
+
+.. code-block:: bash
+
+    cd web/
+    $ php -S localhost:8000
+
+Then see webpage in browser:
+
+    http://localhost:8000/random/10
+
 Hey, that looks a lot like a *traditional* Symfony application! You're right: the
 ``MicroKernelTrait`` *is* still Symfony: but you can control your structure and
 features quite easily.