createPinia failed in Vue 2

[Louis-Tian]

Reproduction

https://codesandbox.io/s/competent-tree-bvzyvk?file=/src/main.js

Steps to reproduce the bug

Basic setup with latest vue2
Follow the instruction here https://pinia.vuejs.org/getting-started.html
using

import { createPinia, PiniaVuePlugin } from 'pinia'

Vue.use(PiniaVuePlugin)
const pinia = createPinia()

Expected behavior

should run without error

Actual behavior

the store failed to initialize with error

TypeError
(0 , $csb__vue_demi.effectScope) is not a function
```an 

### Additional information

_No response_

[Liwoj]

Seems related to this issue - ie. Vue Demi failing in Vue 2 mode in the environment that does not allow postinstall hook to run (as CodeSandbox or Stackblitz)

[posva]

You have starters at https://github.com/piniajs/example-vue-2-vite/

[ebisbe]

I have a similar error:

pinia.mjs:1005 Uncaught TypeError: undefined is not a function
    at createPinia (pinia.mjs:1005:1)
    at ./app/javascript/pos/index.js (index.js:44:1)
    at __webpack_require__ (bootstrap:19:1)
    at ./app/javascript/packs/pos.js (ScreenSize.js:1:1)
    at __webpack_require__ (bootstrap:19:1)
    at bootstrap:83:1
    at bootstrap:83:1 

With Vue 2 with webpack instead of Vite

[posva]

You probably need to tell webpack how to handle .mjs extensions: https://github.com/piniajs/vue-3-cli-webpack-4/blob/main/vue.config.js

• Can't import the named export from non EcmaScript module (only default export is available) #675