Of course, there are not gigs. I know nothing of gigs to be honest.
Upwork. Create a profile as a technical writer, and put links to your docs.
I've picked up partime gigs for API documentation, product usage documentation / User Guide, with screenshots and gifs on that platform. If you are US based, even better cos lot of Companies want to hire US based freelancer for TAX reasons and what not.
Upwork search for client even has a filter that says "US only" and I've used that as a client also, to hire freelancers from within US.
Besides traditional technical writing, there are also gigs for Technical blog posts on various subjects. Avoid the one-off gigs that are low paying, and focus on startups or companies that have already paid for other gigs (you can see it in their profile).