This is the source code of my personal website: https://www.mejibyte.com.
It is written in Jekyll and hosted on GitHub Pages.
$ ./server.sh
$ open $(bundle info --path minima)
Then copy any file from that directory to local repo. For example:
$ cp $(bundle info --path minima)/_includes/header.html ./_includes/header.html
More details: https://jekyllrb.com/docs/themes/#overriding-theme-defaults