feat: add named export in cjs format file

[zhangyuang]

export default has many bugs when mixed with commonjs, vuex use export default object in vuex.cjs.js which behavior is not like vue-router-next. It cause the below code cannot get correct value in the lastest vite version

import { createStore } from 'vuex'
console.log(createStore === undefined)

[zhangyuang]

vuex.cjs.js export code

[zhangyuang]

vue-router-next export code

[zhangyuang]

cc @kiaking , the problem affect users who used the latest vite in ssr