index.json里面的引入到组件名是xr-start，index.wxml这里用的组件是xr-ar-camera

https://developers.weixin.qq.com/miniprogram/dev/framework/xr-frame/#%E5%9C%A8%E9%A1%B5%E9%9D%A2%E4%B8%AD%E4%BD%BF%E7%94%A8%E8%BF%99%E4%B8%AA%E7%BB%84%E4%BB%B6