chore: update composer.json

Add `ext-pcov` extension in `require-dev` so it's properly loaded by nix.

Author: drupol

composer.json

@@ -10,8 +10,8 @@
         }
     ],
     "require": {
-        "php": ">= 7.1.3",
-        "friendsofphp/php-cs-fixer": "^3.12",
+        "php": ">= 7.4",
+        "friendsofphp/php-cs-fixer": "^3.13.2",
         "symfony/yaml": "^3 || ^4 || ^5 || ^6"
     },
     "autoload": {
@@ -31,6 +31,7 @@
         }
     },
     "require-dev": {
+        "ext-pcov": "*",
         "friends-of-phpspec/phpspec-code-coverage": "^6",
         "php-parallel-lint/php-parallel-lint": "^1.3",
         "phpro/grumphp": "1.1.* || 1.3.* || 1.4.* || 1.13.*",