Editing `configuration.yaml` et al. using `vi` via `kubectl exec` is
rather tedious, since the version of `vi` in the *home-assistant*
container image is very rudimentary. Thus, I think it would be better
to use a ConfigMap to store the manually-edited YAML files, so I can
edit them with my regular editor on my desktop. For this to work, the
ConfigMap has to be mounted as a directory rather than as individual
files (using `subPath`), as otherwise the pod would have to be restarted
every time one of the files is updated.