add sass support

package.json

@@ -10,8 +10,10 @@
     "@types/node": "^12.0.0",
     "@types/react": "^16.9.0",
     "@types/react-dom": "^16.9.0",
+    "node-sass": "^4.13.0",
     "react": "^16.12.0",
     "react-dom": "^16.12.0",
+    "react-router-dom": "^5.1.2",
     "react-scripts": "3.3.0",
     "typescript": "~3.7.2"
   },

src/App.tsx

 import React from 'react';
 import logo from './logo.svg';
-import './App.css';
+import './App.scss';
 
 const App: React.FC = () => {
   return (

src/index.tsx

 import React from 'react';
 import ReactDOM from 'react-dom';
-import './index.css';
+import './index.scss';
 import App from './App';
 import * as serviceWorker from './serviceWorker';