Uptake pollyfill for symbol and asyncIterator (#6)

* use conversation from proxy

* Import symbol and asyncInterator from core-js

* reset index.directline

package.json

@@ -15,6 +15,7 @@
     "@babel/plugin-transform-runtime": "^7.9.0",
     "@babel/preset-env": "^7.9.0",
     "@babel/preset-typescript": "^7.9.0",
+    "@types/core-js": "^2.5.3",
     "babel-plugin-istanbul": "^6.0.0",
     "babel-plugin-transform-inline-environment-variables": "^0.4.3",
     "concurrently": "^5.1.0",

src/utils/createAsyncIterableQueue.ts

@@ -1,8 +1,11 @@
 /// <reference path="../types/external.d.ts" />
 
-import createDeferred, { DeferredPromise } from 'p-defer-es5';
-import is from 'core-js/features/object/is';
+import 'core-js/features/symbol';
+import 'core-js/features/async-iterator';
 
+import createDeferred, { DeferredPromise } from 'p-defer-es5';
+
+import is from 'core-js/features/object/is';
 import rejectOnAbort from './rejectOnAbort';
 
 export type AsyncIterableQueue<T> = {