Polyfill
https://github.com/taylorhakes/promise-polyfill/releases
https://cdn.jsdelivr.net/npm/promise-polyfill@8.2.0/dist/polyfill.min.js

Fetch
https://github.com/github/fetch/releases
https://cdnjs.cloudflare.com/ajax/libs/fetch/2.0.4/fetch.min.js
NOTE! Fetch 3.0.0 not work in IE11 - https://github.com/github/fetch/issues/656