写插件菜单时要注意大小写

{
  "name": "hello-world",
  "version": "0.0.1",
  "description": "一份简单的扩展包",
  "author": "Cocos Creator",
  "main": "main.js",
  "main-menu": {
    "Packages/Hello World": {
      "message": "hello-world:say-hello"
    }
  }
}

　　hello-world目录名必须为小写，支持-连接符