whatwg-fetch-mp v3.6.19-fix.1

Forked

Forked from https://github.com/JakeChampion/fetch

Why

仅用于Taro，且仅对微信小程序做了测试

该库是为了在小程序环境顺利使用fetch的polyfill

微信小程序不是真实的浏览器环境，没有fetch 和 XMLHttpRequest 这些全局api。

如需在微信小程序中使用fetch，需要实施以下步骤

1. 安装 @tarojs/plugin-http，该插件polyfill了 XMLHttpRequest
2. 安装 whatwg-fetch-mp，该库针对Taro环境做了一点点适配，能够保证fetch方法顺利使用XMLHttpRequest兜底。

Only for Taro, and only tested on WeChat mini program

This library is a polyfill for smoothly using fetch in a mini program environment.

WeChat mini program is not a real browser environment and does not have global APIs such as fetch and XMLHttpRequest.

If you want to use fetch in WeChat mini program, you need to implement the following steps

1. Install @tarojs/plugin-http, which polyfills XMLHttpRequest
2. Install whatwg-fetch-mp. This library has been slightly adapted to the Taro environment, which can ensure that the fetch method uses XMLHttpRequest smoothly.