chore(package): update eslint-config-react-app to version 4.0.0 (#216)

Author: greenkeeper[bot]

package.json

@@ -138,7 +138,7 @@
     "concurrently": "^4.1.0",
     "coveralls": "^3.0.3",
     "eslint": "^5.15.2",
-    "eslint-config-react-app": "^3.0.7",
+    "eslint-config-react-app": "^4.0.0",
     "eslint-plugin-flowtype": "^3.2.1",
     "eslint-plugin-import": "2.17.2",
     "eslint-plugin-jsx-a11y": "^6.2.1",