While this may be perhaps a little late for the OP, I hope the next person looking for this finds it useful.

CrafterCMS requires a server than can run java and mariadb for the authoring environment, and java for the delivery environment (CrafterCMS doesn't support static delivery by itself, but you can point next.js or Gatsby at it to pull content down if you want to run a static site).

CrafterCMS supports several different deployment models (from unzip-and-go to docker to cloud-native) but neither the UI nor the delivery engine can run inside GitHub. (It works great on a Raspberry Pi 5 though).

Crafter uses git as its datastore, and that datastore can be synchronized (pushed) up to a remote server like GitHub, GitLab, BitBucket, etc. You can then use those servers to facilitate deployment to other environments or collaborate with teammates. They call this DevContentOps.