Welcome @scguffanti and congrats on the launch of Rocket Phonics Foundation! It looks like a very interesting mission to help with literacy.
The GitHub integration is built right in to Replit. There are some official docs on it and also I shared a guide that may help get you in the right direction as well. If you have detailed questions, feel welcome to start a new thread here in the Replit forum and I am sure we can try to help out!
Replit doc: Replit Docs
One of my posts on GitHub sync: You can 'back up' (sync) your Replit code to GitHub