The documentation consists of a collection of markdown text files, with the root of the file hierarchy at docs/mkdocs/src, starting with docs/mkdocs/src/index.md. You can read the documentation as text, with any text viewer or your favorite markdown viewer, or generate a static HTML "site" using mkdocs, which you can then open with any browser.
MkDocs is used to generate a static HTML documentation site. The mkdocs directory contains all the data (actual documentation) and metadata (configuration) for the site. mkdocs/requirements.txt includes the list of Python packages needed to build the site. mkdocs/mkdocs.yml contains the site configuration. mkdocs/src/ is the directory where the actual documentation text, in markdown format, is located.
To build, from the project's root directory:
$ mkdocs build -f docs/mkdocs/mkdocs.yml
You can then open docs/mkdocs/site/index.html with any web browser.