react-warning-cant-call-setstate-on-an-unmounted-component: AbortController Section

[rwieruch]

https://github.com/rwieruch/blog_robinwieruch_content/blob/master/react-warning-cant-call-setstate-on-an-unmounted-component.md

Add alternative solution with AbortController + Fetch. It could be another section of the article as alternative to the _isMounted approach.

See https://github.com/robertoachar/react-fetch-abort-controller/blob/master/src/components/App.jsx