Add Vagrant Cloud account

Vagrant Cloud has been used for years by arch-boxes[1] for publishing
Vagrant boxes. Access to the organization[2] was handed out to a few
members of the DevOps team and the creator of the organization
(arch-boxes maintainer at the time).

With this commit the control of the organization is handed over to the
DevOps team through a new Vagrant Cloud account.

[1] https://gitlab.archlinux.org/archlinux/arch-boxes
[2] https://app.vagrantup.com/archlinux/