Update: copy index.html -> 404.html in build command.

Author: raikusy

package.json

@@ -14,7 +14,7 @@
   },
   "scripts": {
     "start": "react-scripts start",
-    "build": "react-scripts build && cp ./build/index.html ./build/404.html",
+    "build": "react-scripts build && cp build/index.html build/404.html",
     "test": "react-scripts test --env=jsdom",
     "eject": "react-scripts eject"
   },