the devkit setup guide should talk more about ruby versions

[binford2k]

Page: https://docs.openvoxproject.org/ecosystem/latest/devkit/setup.html

#368 has a bit about installing a current ruby. Instead, that discussion should be elevated to the setup guide. We should talk about when you can / cannot use system ruby and briefly discuss the difference between:

1. system ruby
2. openvox vendored ruby
3. self-managed ruby

We don't need rewrite Ruby's installation guides, but we should definitely give people something to get them started. I think in most cases, we probably just recommend vendored ruby. If we're going to the trouble of packaging it, we might as well be using it! 😜