The original template was from RStudio but required some changes to make it work as html and be published through GitHub. I made this work for a repository about Professional Registration and although I attempted to replicate the changes I made there, I got muddled so starting again I have just taken all the files from my repository to make this template.

install.packages("bookdown")
#install.packages("remotes")
remotes::install_github("rstudio/bslib")

In file _output.yml the following can be changed:

      before: |
        <li><a href="./">Bookdown Template</a></li>
      after: |
        <li><a href="https://github.com/rstudio/bookdown" target="blank">Published with bookdown</a></li>
    edit: https://github.com/Lextuga007/bookdown-template%s

Note that the %s is always required in this url.

rmarkdown::render_site(encoding = 'UTF-8')

Or use the Build Book button that appears with the Build tab (where the tabs read Environment, History, Connections and maybe Git if that's connected.)

To publish through GitHub go to Settings/Pages and change Source to main and /root. It will take a few minutes to load the pages.

The file that creates the action can be found in the folder .github\workflows and works with a branch that is created using the script (in the Terminal):

git checkout --orphan gh-pages
git rm -rf .
git commit --allow-empty -m 'Initial gh-pages commit'
git push origin gh-pages
git checkout main

Source via Matt Dray's blog on GitHub Actions and packages.