feature: Allow mount host files/folder

This allow to mount host files into the container see https://docs.gitlab.com/runner/executors/kubernetes.html#using-volumes E.g.:

[[runners.kubernetes.volumes.host_path]]
  name = "shm"
  mount_path = "/dev/shm"
  host_path = "/dev/shm"

NOTE: IF there is a better solution, let me know it

Why do I need this?: Too run selenium