Include egg variables in the output from the API

app/Transformers/Api/Client/EggVariableTransformer.php

@@ -0,0 +1,33 @@
+<?php
+
+namespace Pterodactyl\Transformers\Api\Client;
+
+use Pterodactyl\Models\EggVariable;
+
+class EggVariableTransformer extends BaseClientTransformer
+{
+    /**
+     * @return string
+     */
+    public function getResourceName(): string
+    {
+        return EggVariable::RESOURCE_NAME;
+    }
+
+    /**
+     * @param \Pterodactyl\Models\EggVariable $variable
+     * @return array
+     */
+    public function transform(EggVariable $variable)
+    {
+        return [
+            'name' => $variable->name,
+            'description' => $variable->description,
+            'env_variable' => $variable->env_variable,
+            'default_value' => $variable->default_value,
+            'server_value' => $variable->server_value,
+            'is_editable' => $variable->user_editable,
+            'rules' => $variable->rules,
+        ];
+    }
+}