Ability to use PVC for caching

[ianks]

We are currently using https://github.com/gencer/cache-buildkite-plugin, which is a great way to cache dependencies between steps. One room for improvement would be to have a shared read/write PVC which we could use to cache the deps easily on different agents.

I'm not sure how exactly this would work with this chart, but figured I would pitch the idea. Does this seem like a reasonable use case?