Add/link updated documentation on packaging and using a finished provider

[blixhavn]

What problem are you facing?

While this repository is adequately documented on how to develop your own provider, I feel like we're on our own when it comes to what is needed to package and finalize the provider - both as an open source project available in the Upbound marketplace, and simply making it work with my own Crossplane installation.

How could Crossplane help solve your problem?

Please review the existing documentation and create an easy to follow path forward, rather than the mix-and-match pieces of information currently available here and there.