Added a class to configure repositories

src/PHP/ComposerConfigRepository.php

@@ -0,0 +1,26 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Kiboko\Component\Dockerfile\PHP;
+
+use Kiboko\Component\Dockerfile\Dockerfile;
+use Kiboko\Component\Dockerfile\Variable;
+
+final readonly class ComposerConfigRepository implements Dockerfile\LayerInterface, \Stringable
+{
+    public function __construct(
+        private string $name,
+        private string $type,
+        private string $url,
+    ) {
+    }
+
+    public function __toString(): string
+    {
+        return (string) new Dockerfile\Run(<<<RUN
+            composer config repositories.{$this->name} {$this->type} {$this->url}
+            RUN
+        );
+    }
+}