We always welcome contributions to the documentation. For minor edits, there is a link at the bottom of each page that will take you straight to the file in Github where you can make the changes and submit a PR without ever leaving the browser.
For more extensive changes or contributions, it would be best to open an issue first to discuss your proposal. You don’t want to do a bunch of work that get’s invalidated by work being done by someone else or which the maintainers do not approve of.
See How to file an Issue for a more in depth discussion of how to create a good issue.