If you want to write something user focused, Rust by Example is a great template to use.

A series of self contained lessons that all build on each other.

If you're doing it for a game engine, you'd probably want to start with the GUI, then some basic scripting (that can go much deeper, but I'd keep it short and share other resources). Once that's out of the way, show some examples of how to import assets, how to manage a project directory, etc.

Keep all of this contained within the framework of making a simple game, so when the reader completes the tutorial/documentation, they have something that they can actually show off.

I also like the Odin docs since it's all one page and shows you features in order.