fix(client): add polyfill explicitly

Previously it was only present because of a chain of dependencies

client/package-lock.json

@@ -3008,6 +3008,15 @@
         }
       }
     },
+    "@babel/polyfill": {
+      "version": "7.11.5",
+      "resolved": "https://registry.npmjs.org/@babel/polyfill/-/polyfill-7.11.5.tgz",
+      "integrity": "sha512-FunXnE0Sgpd61pKSj2OSOs1D44rKTD3pGOfGilZ6LGrrIH0QEtJlTjqOqdF8Bs98JmjfGhni2BBkTfv9KcKJ9g==",
+      "requires": {
+        "core-js": "^2.6.5",
+        "regenerator-runtime": "^0.13.4"
+      }
+    },
     "@babel/preset-env": {
       "version": "7.11.5",
       "resolved": "https://registry.npmjs.org/@babel/preset-env/-/preset-env-7.11.5.tgz",

client/package.json

@@ -7,6 +7,7 @@
   "dependencies": {
     "@babel/plugin-proposal-export-default-from": "^7.10.4",
     "@babel/plugin-proposal-function-bind": "^7.11.5",
+    "@babel/polyfill": "^7.11.5",
     "@babel/standalone": "^7.11.6",
     "@fortawesome/fontawesome": "^1.1.8",
     "@fortawesome/fontawesome-svg-core": "^1.2.30",