Redux browser state sync background

background.js

import { applyMiddleware, createStore } from "redux";
import { createSyncMiddleware, syncStore } from "redux-browser-extension-sync/background";
import rootReducer from "../reducers/index.js";

const syncMiddleware = createSyncMiddleware();

const store = syncStore(createStore(
    rootReducer,
    applyMiddleware(syncMiddleware)
));