All GitHub repositories can be equipped with a Wiki repository, also hosted by GitHub. Internally, this Wiki is actually a separate Git repository (located at github.com/username/repo.wiki.git).
Coordinating changes between these two repositories can be a challenge. The cleanest solution I have found is to move the Wiki into the main repo, treat the real Wiki repo as Read-Only (no edits through the UI), and use a GitHub Action to sync changes from main to the Wiki repo.
This can be easily accomplished using GitHub-Wiki-Action with minimal setup.
See the above action for more configuration options.