[FEATURE] ClamAV/VirusTotal cluster mode

**Plugin(s)**
ClamAV and VirusTotal

**What's needed and why ?**
With high number of file uploads, a cluster of ClamAV and API might be useful to spread the load. We need to document how to achieve this.

**Implementations ideas (optional)**
https://docs.clamav.net/manual/Installing/Docker.html#multiple-containers-sharing-the-same-mounted-databases

Start with the linked ClamAV documentation on multiple containers sharing mounted databases and review how the ClamAV and VirusTotal plugins are configured in this repository. Document a supported cluster setup for handling high upload volume, including the relevant deployment considerations and how users can verify it works.

Written by the indexing model from the issue text.