Laravel and Vue.js are another two that come to mind when it comes to the best documentation. Laravel has done most of the boilerplate leg work for you, and their detailed docs provide you the keys to the car to build just about anything. Vue.js also has great documentation for that simple fact that Evan created Vue.js with the intention of being able to read the docs end to end and understand Vue.js over a single weekend when a developer was off from their frontend job.
Personally I love documentation, but I’ve struggled for years to find a way to write the perfect Stripe level documentation for projects.
If you are interested in creating your own Stripe looking documentation and content right within your app like they do, then please check out what I’ve been working on.
I would love some more support and feedback!
The link to the repo and project are in my bio if you’re interested :)
You know the documentation is good when you can rely on it, and not have to seek out external help in mailing lists, Stack Overflow, et cetera.
In the case of PostgreSQL, I was able to be productive with it completely offline, with just a downloaded copy of the documentation.