chore: update docs for Kubernetes-based host

[wilsonianb]

open questions:

• continue to use manifest or replace with something like Codius service definition?
• replace some/most/all references to ILP with Web Monetization? All payment currently happens with web monetization, but open payments will likely eventually be a supported ILP-based alternative.

TODO:

• instructions to set up a host
  • zero to host (https://github.com/codius/codius-install)
  • deploy codius components to existing Kubernetes cluster

[melissahenderson]

Looks good! After everything is complete, I'll re-review the docs as a whole.