Support custom drives

[jtpio]

Problem

Currently JupyterLite supports custom drives, such as:

• https://github.com/jupyterlab-contrib/jupyterlab-filesystem-access
• https://github.com/jupyterlab/jupyterlab-github/

Could Voici also support custom drives?

Proposed Solution

It would be nice if Voici could also support custom drives.

This could make it easier for deployment fetching their files and notebooks from a custom location.

This might need some configuration to be able to select the drive for a dashboard, which could be done at the addon level.

Additional context

This could be relevant to this upstream issue: jupyterlite/jupyterlite#1041