Added service worker config from CRA4.

client/package.json

@@ -55,7 +55,20 @@
     "reselect": "^4.0.0",
     "sass": "^1.32.8",
     "styled-components": "^5.2.0",
-    "subscriptions-transport-ws": "^0.9.18"
+    "subscriptions-transport-ws": "^0.9.18",
+    "web-vitals": "^0.2.4",
+    "workbox-background-sync": "^5.1.3",
+    "workbox-broadcast-update": "^5.1.3",
+    "workbox-cacheable-response": "^5.1.3",
+    "workbox-core": "^5.1.3",
+    "workbox-expiration": "^5.1.3",
+    "workbox-google-analytics": "^5.1.3",
+    "workbox-navigation-preload": "^5.1.3",
+    "workbox-precaching": "^5.1.3",
+    "workbox-range-requests": "^5.1.3",
+    "workbox-routing": "^5.1.3",
+    "workbox-strategies": "^5.1.3",
+    "workbox-streams": "^5.1.3"
   },
   "scripts": {
     "analyze": "source-map-explorer 'build/static/js/*.js'",
@@ -68,7 +81,10 @@
     "madge": "madge  --image ./madge-graph.svg --extensions js,jsx,ts,tsx --circular ."
   },
   "eslintConfig": {
-    "extends": "react-app"
+    "extends": [
+      "react-app",
+      "react-app/jest"
+    ]
   },
   "browserslist": {
     "production": [