Handling files in plugins

I was looking at the https://docs.joinpeertube.org/contribute-plugins?id=storage which says don’t use the
storageManager for files (since they’d be stored in the database), but there’s no suggestion for how to otherwise work with files in plugins.

I have a particular use-case in mind where being able to upload extra files alongside video files for a client-side plugin to read would be very useful.