update build script

Author: devinryanriota

package.json

@@ -26,7 +26,7 @@
   },
   "scripts": {
     "start": "react-scripts start",
-    "build": "react-scripts build",
+    "build": "react-scripts build && cp build/index.html build/404.html",
     "test": "react-scripts test",
     "eject": "react-scripts eject",
     "postbuild": "rm -rf docs/ && mv build docs/ && cp CNAME docs/"