GitHub runner docs: How to run on LXD cloud

How to run on LXD cloud

This machine charm needs to run on virtual machines with nested virtualization enabled.

By default, juju machines on LXD are containers.

To run this charm on LXD, add virt-type=virtual-machine to the constraints during deployment:

juju deploy github-runner --constraints="cores=2 mem=16G virt-type=virtual-machine" --config token=<TOKEN> --config path=<OWNER/REPO>

This constraint ensures the juju machine hosting the charm is a LXD virtual machine. See Managing resource usage for recommendation on cores and mem constraint.