Polyfill CDN 服务 polyfill.io 被中国菠菜 CDN 收购：
https://github.com/polyfillpolyfill/polyfill-service/issues/2834
Cloudflare 提供了一个 alternative endpoint： https://blog.cloudflare.com/polyfill-io-now-available-on-cdnjs-reduce-your-supply-chain-risk