Update symfony 4 project structure

Readme example uses Symfony 2/3 project structure. Update it to Symfony 4+

Author: juanmiguelbesada

bundles/best_practices.rst

@@ -306,26 +306,15 @@ following standardized instructions in your ``README.md`` file.
  ### Step 2: Enable the Bundle
 
  Then, enable the bundle by adding it to the list of registered bundles
- in the `app/AppKernel.php` file of your project:
+ in the `config/bundles.php` file of your project:
 
  ```php
- // app/AppKernel.php
-
- // ...
- class AppKernel extends Kernel
- {
- public function registerBundles()
- {
- $bundles = [
- // ...
- new <vendor>\<bundle-name>\<bundle-long-name>(),
- ];
-
- // ...
- }
+ // config/bundles.php
 
+ return [
  // ...
- }
+ <vendor>\<bundle-name>\<bundle-long-name>::class => ['all' => true],
+ ];
  ```
 
  .. code-block:: rst
@@ -362,26 +351,14 @@ following standardized instructions in your ``README.md`` file.
  ~~~~~~~~~~~~~~~~~~~~~~~~~
 
  Then, enable the bundle by adding it to the list of registered bundles
- in the ``app/AppKernel.php`` file of your project::
-
- // app/AppKernel.php
-
- // ...
- class AppKernel extends Kernel
- {
- public function registerBundles()
- {
- $bundles = [
- // ...
-
- new <vendor>\<bundle-name>\<bundle-long-name>(),
- ];
+ in the ``config/bundles.php`` file of your project::
 
- // ...
- }
+ // config/bundles.php
 
+ return [
  // ...
- }
+ <vendor>\<bundle-name>\<bundle-long-name>::class => ['all' => true],
+ ];
 
  .. _`installation chapter`: https://getcomposer.org/doc/00-intro.md