Add ci.yml. Move App component to separate file.

.github/workflows/ci.yml

@@ -0,0 +1,18 @@
+name: React-CI
+
+on: [push, pull_request]
+
+jobs:
+  build:
+    runs-on: ubuntu-latest
+
+    steps:
+    - uses: actions/checkout@v3 # Using the latest version of the checkout action
+    - name: Set up Node.js
+      uses: actions/setup-node@v5 # Updated to use v5
+      with:
+        node-version: '20' # Specifying Node.js version 20
+    - name: Install Dependencies
+      run: npm install
+    #- name: Run Tests
+    #  run: npm test

src/App.js

@@ -0,0 +1,7 @@
+
+function App()
+{
+    return <h1>Hi there!</h1>;
+}
+
+export default App

src/index.js

@@ -1,13 +1,9 @@
 import React from 'react';
 import ReactDOM from 'react-dom/client';
+import App from './App'
 
 const el = document.getElementById('root');
 
 const root = ReactDOM.createRoot(el);
 
-function App()
-{
-    return <h1>Hi there!</h1>
-}
-
 root.render(<App />);