Ubi example

[anderbubble]

Build on the original work from @th-hummel submitted in #89 and convert to fit in with other examples/.

[th-hummel]

Seems good to me.

Some minor details :

1. Did not play with RHEL 9 though and even with earlier versions I think I witnessed the dnf subscription-manager plugin both mention and not mention (I don't remember if it was depending on RH major version) the so called 'container mode' so I'm not sure if it's still a thing

2. The whole point of my initial reasoning to use ubi from the start (instead of building my own container) was I was not sure bind mounting rhsm registrations info was 100% RedHat supported (feels hacky though it works)

Thanks