Flow-typed: Add AbortController and AbortSignal

[Haroenv]

Documentation is visible here: https://developer.mozilla.org/en-US/docs/Web/API/AbortController/AbortController

I'd like to add it, but not too sure in which files

[Jahans3]

Bump. Is there any update on this?

[AndrewSouthpaw]

You can add it under the browser folder, which is for "libraries" that aren't in NPM.

[stereobooster]

// translation of https://dom.spec.whatwg.org/#abortcontroller
declare interface AbortSignal extends EventTarget {
  +aborted: boolean;
  onabort: EventHandler;
}
declare class AbortController {
  +signal: AbortSignal;
  abort: () => void;
}