There are no "docs". You can read the README of the GitHub project to see how to install and customize it.
The most simple way to understand this project is to read the source code.
Note that this is only a "frontend" project : there are no backend like Django, Rails or Laravel. All the authentication screen are purely "fake" screen : nothing is read from the user inputs.
Therefore, the code itself should be quite easy to follow and understand (I hope). There are no algorithms.
However, if something is not clear, feel free to reach me, or submit an issue on GitHub, I will try to document it somewhere.