https://github.com/tmpvar/jsdom/blob/master/Changelog.md#400

ADDED preliminary support for the Fetch API (https://fetch.spec.whatwg.org/)

ADDED you can use the `browser.fetch` to retrieve any resources, using the
cookies, pipeline and all other browser settings

CHANGED upgraded to JSDOM 4.1

CHANGED use `browser.status` instead of `browser.statusCode` (HTML APIs use
`status` and `statusText`)

CHANGED `browser.resources` is now just an array of all resources requested when
processing the currently open window.  Resources no longer shared by all
windows, and other features (pipeline configuration, fetch resources) moved
elsewhere.

CHANGED separated pipeline from resources.  Use `browser.pipeline.addHandler` to
add request/response handler to the browser instance, or `Pipeline.addHandler`
to add handler to all new instances.

CHANGED pipeline API changed as well.  Request handler called with browser
instance and Fetch `Request` object, can return null or a Fetch `Response`
object.  Response handler called with browser instance, request and response
object, should return same or new response object.  Handlers no longer using
callbacks, if you need asynchronous behavior, return a promise.

FIXED empty `cookie` and `referer` header no longer sent #881

FIXED added `navigator.appVersion` #885

REMOVED `document.window`, use `document.defaultView` instead

REMOVED `browser.close` confusing method name, use `browser.window.close` if you
really need to close the window.

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