Add song to library from "document provider" sources

[phirestalker]

In other apps I am able to choose files from my linked Dropbox, Google Drive, Nextcloud, etc. I have learned that these are called document providers.

I would like to be able to add these "folders" to be scanned by your app for music. I would hope it would basically allow me to use your local music player app as a cloud music player app without your app having to support dozens of cloud providers.