Changelog
Changelog (or release notes) helps developers to stay up to date with project changes and helps migrating to new versions.
Documentation is an important part of any software product. Even though creating it may not be as much fun as writing code, to users it's how software feels when they get started.
GitHub's 2017 Open Source Survey found that the biggest problem encountered in open source was "incomplete or confusing documentation." The top insight from the survey: "Documentation is highly valued, frequently overlooked, and a means for establishing inclusive and accessible communities.
Changelog (or release notes) helps developers to stay up to date with project changes and helps migrating to new versions.
Tutorial is great way to help user to get started. It takes user through a series of steps demonstrating a particular use case, introduces the main project concepts and shows how to apply them. Tutorial is the first entry point for many developers and is a critical part of project's developer experience.
Code block is the key element of any documentation. Developers often read and use code without looking at explanations around. So make sure code block itself provides enough information to be understood and correctly reused.
Online playground allows to edit and execute code right from the browser. It makes documentation interactive and builds an engaging onboarding experience. While it won't work for many projects, be sure to explore your options - you may be surprised!
Reproducing examples from documentation can be a tedious process. Let the reader see the result of code execution without leaving the docs.