chore: add husky for automatic linting of staged files (#938)

package.json

@@ -99,6 +99,17 @@
     "workbox-webpack-plugin": "^4.3.1",
     "worker-loader": "^2.0.0"
   },
+  "husky": {
+    "hooks": {
+      "pre-commit": "lint-staged"
+    }
+  },
+  "lint-staged": {
+    "src/**/*.{js,json,css}": [
+      "prettier --write",
+      "git add"
+    ]
+  },
   "resolutions": {
     "**/@babel/runtime": "7.5.5"
   }