chore(dependencies): update for symfony

Drop support for PHP 7.3, add PHP 8.1. Drop support for legacy symfony versions, add support for new version 6.

close #21

Author: m-bymike

composer.json

@@ -17,9 +17,9 @@
     ],
     "bin": ["bin/xmllint"],
     "require": {
-        "php": "7.3.*|7.4.*|8.0.*",
-        "symfony/console": "3.4.*|4.4.*|5.*",
-        "symfony/finder": "3.4.*|4.4.*|5.*",
+        "php": "7.4.*|8.0.*|8.1.*",
+        "symfony/console": "4.4.*|5.3.*|5.4.*|6.*",
+        "symfony/finder": "4.4.*|5.3.*|5.4.*|6.*",
         "ext-libxml": "*",
         "ext-dom": "*"
     },