Add AbortController and AbortSignal polyfill

[DavidBruant]

A feature request

What

polyfill.io does not provide polyfills for AbortController and AbortSignal
consequently, it also does not provide support for abortable fetch

The feature exists and is supported in recent browsers, but lacks support in (current at time of writing) Safari 12 and webkit-based mobile browsers like Chrome on iOS and Firefox on iOS

Details

There is an existing MIT-licenced polyfill

I'm not sure whether "AbortController + AbortSignal" and "abortable fetch" should be made into two separate issues

Additional information

i love the polyfill.io project <3
thank you very very much

[JakeChampion]

Hi @DavidBruant, thank you for the kind words!

We have a pull-request for this feature already :-) It is actively being worked on and I hope to have it in the next release of the polyfill-library. #59

[JakeChampion]

this was added in #59