sync iterator polyfill

package-lock.json

 {
   "name": "mycard-mobile",
-  "version": "1.0.22",
+  "version": "1.0.23",
   "lockfileVersion": 1,
   "requires": true,
   "dependencies": {
@@ -1931,8 +1931,7 @@
     "core-js": {
       "version": "2.5.7",
       "resolved": "https://registry.npmjs.org/core-js/-/core-js-2.5.7.tgz",
-      "integrity": "sha512-RszJCAxg/PP6uzXVXL6BsxSXx/B05oJAQ2vkJRjyjrEcNVycaqOmNb5OTxZPE3xa5gwZduqza6L9JOCenh/Ecw==",
-      "dev": true
+      "integrity": "sha512-RszJCAxg/PP6uzXVXL6BsxSXx/B05oJAQ2vkJRjyjrEcNVycaqOmNb5OTxZPE3xa5gwZduqza6L9JOCenh/Ecw=="
     },
     "core-util-is": {
       "version": "1.0.2",

package.json

@@ -24,6 +24,7 @@
     "@angular/pwa": "^0.6.8",
     "@angular/router": "6.0.5",
     "@angular/service-worker": "6.0.5",
+    "core-js": "^2.5.7",
     "font-awesome": "^4.7.0",
     "hammerjs": "^2.0.8",
     "lodash": "^4.17.10",

src/polyfills.ts

@@ -40,10 +40,10 @@
 /** IE10 and IE11 requires the following for the Reflect API. */
 // import 'core-js/es6/reflect';
 
-
 /** Evergreen browsers require these. **/
 // Used for reflect-metadata in JIT. If you use AOT (and only Angular decorators), you can remove.
 // import 'core-js/es7/reflect';
+import 'core-js/fn/symbol/async-iterator';
 
 
 /**