Dear Maintainer,

The "Locations of WirePlumber’s files" page refers to XDG environment
variables (such as $XDG_DATA_HOME) in several places, and links to the
specification.  However, it doesn't say what happens if one of those
variables is not set.  The specification says a default "should" be
used, which is to say that using a default is optional.

WirePlumber does seem to use the default values, and that should be
documented.

- Michael