The mermaid directory contains the mermaid files which serve as the source code for the svg files included in the ../errors.md
To generate these files, there is an included script, build_images.sh which builds images for all the mermaid files in the mermaid directory.
To use this script, the mermaid cli must be installed and be accessible via your $PATH variable.
Note on mermaid installation
It is preferable to install mermaid via npm rather than brew since brew will install node as a dependency which could interfere with nvm.