GitHub is designed for "2-player" development. You can draft and build games together using these features: Draft Pull Requests Draft Pull Requests
If your game involves a card or character "draft," you can implement a standard 2-person drafting system: Winston Draft 2 player githubio free
This article will break down everything you need to know: what GitHub.io is, why it’s safe and free, and the absolute best 2-player games you can play right now. GitHub is designed for "2-player" development