Prevents React App from Flash During Firebase/API Calls

const store = createStore(     rootReducer,     compose(         applyMiddleware(             thunk.withExtraArgument({                 getFirestore,                 getFirebase             })         ),         reduxFirestore(fbConfig),         reactReduxFirebase(fbConfig, { attachAuthIsReady: true }),         window.__REDUX_DEVTOOLS_EXTENSION__         && window.__REDUX_DEVTOOLS_EXTENSION__()     ) );

store.firebaseAuthIsReady.then(() => {     ReactDOM.render(         <Provider store={store}>             <App />         </Provider>,         document.getElementById('root')     ); });