Is it possible to create a github pages subdomain with the project instead of username as in project_name.github.io
I do not think so. It only the basic tutorial for creating one, located here, says that you have to use
Ok thank you for the reply.
You can create an organisation using the project name (if it’s available), and then build the pages repo there. You’ll be able to use the
organisation_name.github.io pages URL then.
Alternately, you can also assign a custom domain if you own one.