First, you need switch to gh-graph branch.
To run Jekyll in a way that matches the GitHub Pages build server, run Jekyll with Bundler.
Use the command bundle exec jekyll serve in the root of your repository (after switching to the gh-pages branch for project repositories),
and your site should be available at http://localhost:4000. For a full list of Jekyll commands, see the Jekyll documentation.
The detail can refer to Using Jekyll with Pages