How about developing and supporting a browser extension for some company? Have you researched what extensions are able to do? For example extensions for VPN service which is never free. I would like to pay for adBlock if it becomes paid, I do not use any other extension regularly.
VPN and adblock are good examples of extensions that give real value to the user. When it comes to writing code for someone, I was more interested in the idea for a startup and its business model.
VPN is not just a browser extension, this is properly configured someone's computer and an improper way of receiving VPN service.
Adblock is also not just a browser extension, this is a result of some community willing to reverse engineer whatever the web throws at me.