I love the project! I see two different issues that might make this process a little harder than it needs to be. The first one is the whole git process, and the other is the notebook stripout that needs to be done, apparently it can get very messy if you don’t strip-out the notebook when you push them to github.
here is an article about using using notebooks and git.
fast.ai has a nice tutorial on notebook stripout on how to do it for the fast ai library, I am assuming that we could modify that for your repo.
If you are interested in a fairly easy process to get started with git, I made a tutorial for fast.ai(don’t use this for notebooks) how to create a PR(pull request).
I think it might be easier to have one person update the notebook in the repo,and everyone that wants to make additions, could create a gist and share it here, the maintainer of the repo could update the notebook manually. How to create a gist
It might be even easier to use use google colab instead of github. Everyone could just share the file. There are limitation but it is far less complicated for beginners.