This repository contains a custom version of plugin-highlight for the Arcane Algorithm Archive. The only change so far is that it utilizes our custom version of highlight.js. If you want to use plugin-highlight for your own project, then you should probably use the official version or find a fork that's being actively maintained.
This plugin is the default GitBook plugin used to highlight code blocks.
You can remove it using:
{
plugins: ["-highlight"]
}