react-java-mysql: use create-react-app for frontend

Signed-off-by: Jérémie Drouet <jeremie.drouet@gmail.com>

react-java-mysql/frontend/src/App.tsx

@@ -0,0 +1,43 @@
+import React, { useEffect, useState } from "react";
+import logo from "./logo.svg";
+import "./App.css";
+
+type Greeting = {
+  id: number;
+  name: string;
+};
+
+function App() {
+  const [greeting, setGreeting] = useState<Greeting>();
+  useEffect(() => {
+    fetch("/api")
+      .then(res => res.json())
+      .then(setGreeting)
+      .catch(console.error);
+  }, [setGreeting]);
+  return (
+    <div className="App">
+      <header className="App-header">
+        <img src={logo} className="App-logo" alt="logo" />
+        {greeting ? (
+          <p>Hello from {greeting.name}</p>
+        ) : (
+          <p>Loading...</p>
+        )}
+        <p>
+          Edit <code>src/App.tsx</code> and save to reload.
+        </p>
+        <a
+          className="App-link"
+          href="https://reactjs.org"
+          target="_blank"
+          rel="noopener noreferrer"
+        >
+          Learn React
+        </a>
+      </header>
+    </div>
+  );
+}
+
+export default App;