tl;tr

In repository settings, enable GitHub Pages for the master branch.

Now you can access your site at https://your-username.github.io/your-repo-name

Done. Period.

How

GitHub Pages will use README.md as index page.And your project probably already have one.There is no need to write index.html or index.md.

Also, GitHub Pages will automatically add an “edit on GitHub” link to page footer.Nice.

Why

Focus on content, not the site design and configuration.

We use README.md and master branch.This makes updating project site easier.Just update README.md without the hassles of sync documentation between master and gh-pages branches.

Bonus

Your project may have some additional documentary pages.They are welcome by GitHub Pages.

For example:

README.md
...
docs/
    README.md
    quick-start.md
    install/
    linux.md
    osx.md
    bsd.md
    win.md

URL paths will be:

/index.html
/docs
/docs/quick-start.html
/docs/install/linux.html
/docs/install/osx.html
/docs/install/bsd.html
/docs/install/win.html

Conclusion

Yes. You can have a site powered by GitHub Page up and runningwithout writing a single line ofyaml configuration, html template, css, javascript, etc.