Improve documentation for bosh deployment.

[haydonryan]

Is your feature request related to a problem? Please describe.

I'm trying to follow along with https://github.com/concourse/concourse-bosh-deployment/blob/master/cluster/README.md
To deploy concourse in my homelab.
It's been forever since I've used this deployment repo, and I can't recall what the versions.yml is used for.

Adding this issue as I might have a go at adding some more documentation. Also the examples should be to run the bosh deploy outside of this repo like bosh-deployment does.

Describe the solution you'd like

as above

Describe alternatives you've considered

No response

Additional context

No response

[haydonryan]

We should also state that we require the jammy stemcell as a prerequisite