Tutorial demonstrating how to structure programs

This is related to https://github.com/typelevel/cats-effect/issues/3031, since sharing state and composing resources is tangled with understanding programs-as-values :)

@davesmith00000 for example points to the documentation for Queue: it doesn't do a bad job demonstrating how to make a Queue and how to use it. But figuring out how to work it into your program structure and share it is actually non-trivial, and the example doesn't really demonstrate that at all.

We already have the fantastic kitteh-redis example which certainly demonstrates how to architect a real-world program. I understand has an organic commit history. So possibly it just needs to be accompanied by a written walkthrough/tutorial: it's hard to know where to jump in and start from!

Start with the existing Queue documentation and the kitteh-redis example linked in the issue, noting how they demonstrate resource creation, sharing, and program structure. Done means adding a written walkthrough that gives newcomers a clear place to start and explains how these pieces fit together.