Documented how to use a mercure hub when using the docker image

config/test/test_config.global.php

@@ -79,13 +79,17 @@ return [
             'process-name' => 'shlink_test',
             'options' => [
                 'pid_file' => sys_get_temp_dir() . '/shlink-test-swoole.pid',
-                'worker_num' => 1,
-                'task_worker_num' => 1,
                 'enable_coroutine' => false,
             ],
         ],
     ],
 
+    'mercure' => [
+        'public_hub_url' => null,
+        'internal_hub_url' => null,
+        'jwt_secret' => null,
+    ],
+
     'dependencies' => [
         'services' => [
             'shlink_test_api_client' => new Client([