Side note, how do I volunteer or work part time writing technical documentation? I feel like my writing skills and my ability to make code understandable and explicit to other readers would be a perfecy use for producing great documentation.
You can always pick a few projects on GitHub that have a less than ideal readme or set of docs and submit a bunch of PRs at once, I've done that before as a quick way to make myself feel like I'm contributing to the community whenever I don't have the motivation to push through on my own projects.