index.html

    <script src="https://www.gstatic.com/firebasejs/8.6.1/firebase-app.js"></script>
    <script src="https://www.gstatic.com/firebasejs/8.6.1/firebase-firestore.js"></script>

    <script>
      // Your web app's Firebase configuration
      // For Firebase JS SDK v7.20.0 and later, measurementId is optional
      const firebaseConfig = {
        apiKey: "",
        authDomain: "",
        projectId: "",
        storageBucket: "",
        messagingSenderId: "",
        appId: "",
      };

      // Initialize Firebase
      firebase.initializeApp(firebaseConfig);
    </script>

    <script src="main.dart.js" type="application/javascript"></script>