GitHub Sponsors (https://github.com/sponsors) already exists, but I feel that they missed the point. As a user, I don't want to throw money at a project like it's a charity, I want to throw money so issues will be solved. As a developer, I don't want to accept unconditional donations (and all the unwritten, assumed responsibilities it comes with), I want to be funded in a concrete way so I can work on the issues users want so much they'd pay for it.