update react-scripts to 3.4.0

Author: bitworking

example/package.json

@@ -11,7 +11,7 @@
     "react-dom": "^16.4.1",
     "react-gsap": "1.0.16",
     "react-router-dom": "^4.3.1",
-    "react-scripts": "3.0.0",
+    "react-scripts": "3.4.0",
     "react-scrollmagic": "link:..",
     "styled-components": "^3.4.9"
   },