how to choose sessionStorage

this plugin is too simple to use, but some docs is still useful! I can't find a doc, until I searched the issues...

Issue Link

// Example custom build usage:
var engine = require('../store-engine')
var storages = require('store/storages/sessionStorage')

var plugins = []
var store = engine.createStore(storages, plugins)
store.set('foo', 'bar')

ES6 version:

import engine from 'store/src/store-engine';
import sessionStorage from 'store/storages/sessionStorage';

const storages = [sessionStorage];
const plugins = [];
const sessionStore = engine.createStore(storages, plugins);