I could not find any Flux documentation that explains how to create/add a “project document” (or where in the UI to do it) to clear the DRC message “Project has no documentation.” After 3 different searches, nothing relevant came up, which likely means this feature is either not documented or not available in Flux as described by that DRC.
The only relevant documentation entry I found is about using the help tool itself (it does not describe project documents or steps to create them). Source