add index controller

app/api/controller/v1/Index.php

@@ -0,0 +1,12 @@
+<?php
+
+namespace app\api\controller\v1;
+
+use app\api\ApiController;
+
+class Index extends ApiController{
+
+    public function index(){
+        return $this->success('Hello World');
+    }
+}