It would be great if there was an option for publish that allowed adding release notes, something like:
expo publish ... -m "Bug fixes & performance improvements"
Then this could be referenced in the app to let the user why an update was needed, or what new functionality is available.
It could be as simple as a string, or as complicated as an arbitrary object, which would allow fancy things like update types (new feature vs bug fix), title, message, and possibly more.
Another way to handle this is allowing a "What's New" object in app.json.
Now that I write this, I realize I can probably just have a json file with updates in it, but I'll post this anyway in case other people have the same idea.