Define/document method for periodically running data import

[haikoschol]

We have a CLI for importing data now, but we also want to have this run periodically for a given deployed instance of vulnerablecode. This depends on how it is deployed. For a single server it could be a simple cron job. Or we could have some kind of infrastructure-as-code for deploying a database, API server and setting up a periodic import (e.g. for Kubernetes).

The purpose of this issue is to discuss which way to go and either do it (if it amounts to a few changes to the README and some yaml files), or spawn new issues for implementation from it.