To use this file, make a copy and call it
CUSTOMISATIONS.md. Then add details about customisations of the site that would otherwise live in documents or a wiki, external to the site. By keeping the information in the repository, it is readily accessible by everyone working on the site.
Do not add sensitive information such as passwords, key information, or personal information though. The file is committed to the repository for others to have the information available. If your repository were to be made public, the information becomes public as well.
This file sits outside of the htdocs folder so it is not added to a server.