add firebase javascript

1// Create Firebase project
2
3// Create Web app in Firebase console
4
5// Link project
6
7var firebaseConfig = {
8  apiKey: // apiKey,
9  authDomain: // authDomain,
10  databaseURL: // databaseURL,
11  projectId: // projectId,
12  storageBucket: // storageBucket,
13  messagingSenderId: // messagingSenderId,
14  appId: // appId,
15  measurementId: // measurementId
16};
17firebase.initializeApp(firebaseConfig);
18
19// Add your dependencies
20
21//E.G.
22
23<script src="https://www.gstatic.com/firebasejs/7.21.1/firebase-app.js"></script>