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/symfony/css-selector/composer.json

@@ -1,7 +1,7 @@
 {
     "name": "symfony/css-selector",
     "type": "library",
-    "description": "Symfony CssSelector Component",
+    "description": "Converts CSS selectors to XPath expressions",
     "keywords": [],
     "homepage": "https://symfony.com",
     "license": "MIT",
@@ -20,7 +20,8 @@
         }
     ],
     "require": {
-        "php": "^5.5.9|>=7.0.8"
+        "php": ">=7.2.5",
+        "symfony/polyfill-php80": "^1.16"
     },
     "autoload": {
         "psr-4": { "Symfony\\Component\\CssSelector\\": "" },