feat: add customizable store/cache driver option

[OrbisK]

Sometimes I would like to have the possibility to have a custom driver for the pnpm store i.e. to be able to keep the cache in the browsers IndexDB in webcontainers.

The usecase might not be the most used one, but it could make pnpm even more interesting for webcontainers.

I imagine it to be similar to unstorage: https://unstorage.unjs.io/drivers