Support custom host-to-IP mappings via --add-host option

[comunidadio]

Summary

Ability to configure custom hostnames without DNS involvement.

Why

In some internal networks it's handy to have pre-configured entries in /etc/hosts for networking with internal services.

How (optional)

--add-host option similar to Docker's:

--add-host list Add a custom host-to-IP mapping (host:ip).

Hosts passed this way would be added to the guest's /etc/hosts by guest-init.

[sosso]

This would be great for us too; I'm hoping to have some docker containers running on the host made visible to the matchlock container.

[jingkaihe]

Added in release v0.1.20