migration symfony 5 4 (#300)

* symfony 5.4 (diff dev)

* symfony 5.4 (working)

* symfony 5.4 (update autoload)

* symfony 5.4 (remove swiftmailer mailer implementation)

* symfony 5.4 (php doc and split Global accessor class)


### Impacted packages:

composer require php:">=7.2.5 <8.0.0" symfony/console:5.4.* symfony/dotenv:5.4.* symfony/framework-bundle:5.4.* symfony/twig-bundle:5.4.* symfony/yaml:5.4.* --update-with-dependencies

composer require symfony/stopwatch:5.4.* symfony/web-profiler-bundle:5.4.* --dev --update-with-dependencies

lib/psr/container/src/ContainerInterface.php

@@ -1,7 +1,6 @@
 <?php
-/**
- * @license http://www.opensource.org/licenses/mit-license.php MIT (see the LICENSE file)
- */
+
+declare(strict_types=1);
 
 namespace Psr\Container;
 
@@ -20,7 +19,7 @@ interface ContainerInterface
      *
      * @return mixed Entry.
      */
-    public function get($id);
+    public function get(string $id);
 
     /**
      * Returns true if the container can return an entry for the given identifier.
@@ -33,5 +32,5 @@ interface ContainerInterface
      *
      * @return bool
      */
-    public function has($id);
+    public function has(string $id);
 }