Added a default value for the ARG syntax + rename class with Global prefix

Author: sebprt

src/Dockerfile/Arg.php

@@ -8,11 +8,12 @@
 {
     public function __construct(
         private string $name,
+        private string $defaultValue,
     ) {
     }
 
     public function __toString(): string
     {
-        return sprintf('ARG %s', $this->name);
+        return sprintf('ARG %s=%s', $this->name, $this->defaultValue);
     }
 }

src/PHP/ComposerConfig.php renamed to src/PHP/ComposerConfigGlobal.php

@@ -6,7 +6,7 @@
 
 use Kiboko\Component\Dockerfile\Dockerfile;
 
-final readonly class ComposerConfig implements Dockerfile\LayerInterface, \Stringable
+final readonly class ComposerConfigGlobal implements Dockerfile\LayerInterface, \Stringable
 {
     public function __construct(
         private string $host,