add finally polyfill for promises

web/app/common/polyfills.js

@@ -1,5 +1,17 @@
 import 'core-js/es6/promise';
 
+// default promise polyfill doesn't include finally
+Promise.prototype.finally = function finallyFn(callback) {
+  const constructor = this.constructor;
+
+  return this.then(
+    (value) => constructor.resolve(callback()).then(() => value),
+    (reason) => constructor.resolve(callback()).then(() => reason)
+  );
+};
+
+window.Promise = Promise;
+
 export default function loadPolyfills() {
   const fillCoreJs = () => {
     if (

web/package.json

@@ -44,7 +44,9 @@
     "bem-react-helper": "^1.1.2",
     "preact": "^8.2.9"
   },
-  "eslintIgnore": ["public"],
+  "eslintIgnore": [
+    "public"
+  ],
   "jest": {
     "transform": {
       "^.+\\.jsx?$": "<rootDir>/fileTransformer.js"