Add devtools typings

[joseluisq]

Due that Typescript threw me a No declaration file was found for the 'unistore/devtools' module error. This PR fixes it by just adding a devtools.d.ts file.

"unistore": "^3.0.6"

// store.ts
import createStore, { Store } from 'unistore'
import devtools from 'unistore/devtools'

// just like createStore() typing, devtools() will return the `State`
export const store = devtools(createStore({ count: 0 }))
// ...

[developit]

Thanks!

[joseluisq]

👍

[joseluisq]

Hey! I seems like you forgot (v3.1.0) to publish the devtools.d.ts file.

See https://unpkg.com/unistore@3.1.0/