Currently, there's no license specified for the repository, so it's unclear under what license users are receiving the contents, and under which license they are contributing to the repo.

Quoting GitHub:

What happens if I don't choose a license?

You're under no obligation to choose a license. It's your right not to include one with your code or project, but please be aware of the implications. Generally speaking, the absence of a license means that the default copyright laws apply. This means that you retain all rights to your source code and that nobody else may reproduce, distribute, or create derivative works from your work. This might not be what you intend.

Even if this is what you intend, if you publish your source code in a public repository on GitHub, you have accepted the Terms of Service which do allow other GitHub users some rights. Specifically, you allow others to view and fork your repository.

If you want to share your work with others, we strongly encourage you to include an open source license.

Since this is essentially documentation rather than code, perhaps consider using a Creative Commons license? See GitHub's guide to choosing a license.