https://www.indeed.com/q-Technical-Writer-Editor-jobs.html
https://www.flexjobs.com/jobs/technical-writing
https://www.upwork.com/freelance-jobs/technical-editing/
https://www.fiverr.com/search/gigs?query=writing%2Bproof%2Br...
You can also contact agencies like Toptal and Robert Half.
If you want a different type of job then you need to have evidence or a convincing story that you have literally done that job before, either as an intern or through training/education or as projects on your own. But the fact that you have literally done proofreading and documentation editing in a technical context and there is a record on Github seems to be concrete proof that should be possible to leverage into getting paid work doing the same thing.
https://github.com/malgamves/CommunityWriterPrograms
In the process of doing this type of work, you surely will learn new things and probably will help you figure out exactly what you might want to focus on / become an expert at / etc. You'll come to understand systems from a user's perspective which always good for developers.
Just my $0.02.
But if they're accepted by the repo owner, they're probably not nonsense. And projects need better documentation. If the OP was applying for a junior 'tech' role of some sort, and demonstrated that experience of revising documentation to be up to date and improved... it's a step up from some people I've seen over the years (who leave behind bad/broken docs, for example).
This is the kind of thing full time engineers typically don't enjoy doing, so docs stagnate and can quickly become out of date or inaccurate.
It's super useful if someone is used to a routine where they know how to dig into a project, find errors/inaccuracies, and work to improve them.