Fixes https://github.com/github/fetch/issues/801

fixes https://github.com/github/fetch/issues/802

Fixes https://github.com/github/fetch/issues/800

https://github.com/github/fetch/issues/787

Revert "Detect if DOMException exists via typeof instead of trying to call it and catching the exception which may get thrown"

This reverts commit e3298525.

Closes https://github.com/github/fetch/issues/780

Detect if DOMException exists via typeof instead of trying to call it and catching the exception which may get thrown

fixes https://github.com/github/fetch/issues/724

fixes https://github.com/github/fetch/issues/657

Co-authored-by: NJake Champion <me@jakechampion.name>

Co-authored-by: NJake Champion <me@jakechampion.name>

Co-authored-by: NJake Champion <me@jakechampion.name>

Co-authored-by: Nfdacosta <fabio.costa@disneystreaming.com>
Co-authored-by: NJake Champion <me@jakechampion.name>

* Compatibility for fetch-mock using proxy-pollyfill
Fixes wheresrhys/fetch-mock#415

Details: fetch-mock wraps the Response object in an ES6 Proxy to
provide useful test harness features such as flush.  However, on
ES5 browsers without fetch or Proxy support pollyfills must be used;
the proxy-pollyfill is unable to proxy an attribute unless it exists
on the object before the Proxy is created.  This change ensures
Response.bodyUsed exists on the instance, while maintaining the
semantic of setting Request.bodyUsed in the constructor before
_initBody is called.

* Update fetch.js
Co-authored-by: NJake Champion <me@jakechampion.name>

* Change default statusText for Response

* Cleanup test descriptions. Remove redundant tests.

* Remove checking old behavior for statusText default value

Document more common pitfalls in the README

People are getting tripped up on these being unavailable in the polyfill.

I have enabled 2FA for my npm account, and thus CI is not allowed to publish releases on my behalf without my manual intervention.