Just make a new repository using this project as a template - https://docs.github.com/en/repositories/creating-and-managing-repositories/creating-a-repository-from-a-template
Then go to Settings -> Pages tab on the left -> Select gh-pages from the dropdown under Branch and leave the second dropdown as / (root)
If gh-pages isn't there yet then reload the page a few times and it should appear. It takes the github action a moment to build the site and put it into the branch. Alternatively, if you check the box for "Include all branches" when copying from the template then it'll probably already be there.
After a short wait you should be able to access USERNAME.github.io/REPONAME and see a julia set which shows your new regl project is ready to hack on!
npm run dev - run dev server
If you'd like to build under prod mode to test locally:
npm run build - build for prod
But this shouldn't be necessary since you can just use Pages!