Demo doesn't run in Internet Explorer

There are two known issues in Internet Explorer (IE):
1. IE [lacks native Promise support](https://caniuse.com/#search=promise), so you need to add a promise polyfill to get the demo to work in IE.

2. IE tries to download the JSON from the mock API at localhost:3001/users. [Here are some workarounds](https://stackoverflow.com/questions/6114360/ie-prompts-to-open-or-save-json-result-from-server).

首先在 Internet Explorer 中运行 demo，并检查它如何加载依赖 Promise 的代码，以及如何从 localhost:3001/users 处的 mock API 请求 JSON。查看链接的 Promise 支持和 JSON workaround 参考资料，然后验证 demo 是否能在 IE 中成功运行且不会出现下载提示。

由索引模型根据 Issue 内容生成。