fix(config-provider): ensure class_exists before instantiation (#105)

preservefix(config-provider): ensure class_exists before instantiation
Fixed an issue in ConfigProvider where a class was being instantiated
without first checking if it exists. Exists when executing `php bin/hyperf.php server:watch`command

src/ConfigProvider.php

@@ -37,7 +37,7 @@ public function __invoke()
         foreach ($mineJsonPaths as $jsonPath) {
             if (file_exists($jsonPath->getPath() . '/' . Plugin::INSTALL_LOCK_FILE)) {
                 $info = json_decode(file_get_contents($jsonPath->getRealPath()), true);
-                if (! empty($info['composer']['config'])) {
+                if (! empty($info['composer']['config']) && class_exists($info['composer']['config'])) {
                     $provider = (new ($info['composer']['config']))();
                     $initialConfig = array_merge_recursive($provider, $initialConfig);
                 }