Fix IE11 deployment

package.json

@@ -28,11 +28,13 @@
   },
   "browserslist": {
     "production": [
+      "ie 11",
       ">0.2%",
       "not dead",
       "not op_mini all"
     ],
     "development": [
+      "ie 11",
       "last 1 chrome version",
       "last 1 firefox version",
       "last 1 safari version"

src/index.js

@@ -1,4 +1,6 @@
 /* These polyfills are required for IE11 support. */
+import 'react-app-polyfill/ie11';
+import 'react-app-polyfill/stable';
 import 'core-js';
 import 'regenerator-runtime';