You get an error message like this one.
Firebase has recently changed the way they present the integration code. Our docs were showing you just to copy and paste the integration string. But they changed the variable from config to firebaseConfig.
And now when you just copy and paste the code, you get an error like the one above.
The solution is easy.
in Builder/src/config/firebase_config.js instead of
exports.config = config;
at the bottom, you should have
exports.config = firebaseConfig;