fix(package): update react-scripts to version 3.1.2

Closes #13

Author: greenkeeper[bot]

package.json

@@ -6,7 +6,7 @@
     "firebase": "^5.7.0",
     "react": "^16.6.3",
     "react-dom": "^16.6.3",
-    "react-scripts": "3.1.0"
+    "react-scripts": "3.1.2"
   },
   "scripts": {
     "start": "react-scripts start",