Update documentation on how to scan local Debian/Ubuntu OS

[KoenDG]

The documentation here: https://google.github.io/osv-scanner/usage/

Claims this is a preview and doesn't describe how to do it, skipping to the scanning of Docker containers.

Looking at the code a bit, it's not clear to me how it would be done.

[hayleycd]

Thank you for opening an issue. We'll look into it.

[github-actions[bot]]

This issue has not had any activity for 60 days and will be automatically closed in two weeks

[github-actions[bot]]

Automatically closing stale issue

[another-rex]

I believe this is resolved in the documentation here: https://google.github.io/osv-scanner/supported-languages-and-lockfiles/#alpine-package-keeper-and-debian-package-manager

Essentially, you have to specify the lockfile type:

osv-scanner --lockfile 'apk-installed:/lib/apk/db/installed'