Delete jsx files and use tsx ones instead

Author: adzialocha

src/app.jsx

@@ -1,4 +1,4 @@
-import React from "react";
+import React from 'react';
 
 const App = () => <p>Hallo, hier ist alles schön :)</p>;
 

src/app.tsx

@@ -1,8 +1,8 @@
-import "core-js/stable";
-import "regenerator-runtime/runtime";
+import 'core-js/stable';
+import 'regenerator-runtime/runtime';
 
-import React from "react";
-import ReactDOM from "react-dom";
-import App from "./app";
+import React from 'react';
+import ReactDOM from 'react-dom';
+import App from './app';
 
-ReactDOM.render(<App />, document.getElementById("root"));
+ReactDOM.render(<App />, document.getElementById('root'));