Rename example domains to generic scheme

Use example.com instead of domain.de/game references to make
the skeleton truly generic and not tied to any specific project.

www/api.example.com/public/index.php

@@ -0,0 +1,18 @@
+<?php
+/**
+ * api.example.com — REST API
+ */
+header('Content-Type: application/json');
+$method = $_SERVER['REQUEST_METHOD'];
+switch ($method) {
+    case 'GET':
+        echo json_encode(['status' => 'ok', 'message' => 'API läuft']);
+        break;
+    case 'POST':
+        $input = json_decode(file_get_contents('php://input'), true);
+        echo json_encode(['status' => 'received', 'data' => $input]);
+        break;
+    default:
+        http_response_code(405);
+        echo json_encode(['error' => 'Method not allowed']);
+}