Honestly, it might be better to use a realtime collaboration service. If you need to you could automatically sync this with the GitHub version by pulling update

Honestly, it might be better to use a realtime collaboration service. If you need to you could automatically sync this with the GitHub version by pulling updates on a schedule. I've used hackmd.io for real-time collaboration in Markdown. They even offer an open-source self-hosted version, https://github.com/hackmdio/codimd https://github.com/hackmdio/codimd. There may be other services as well.