The README currently states that feedbackd uses the `default.json` theme, whose
location is hardcoded into the application. This doesn't reflect the current
state of the code.
Explain the ability to add custom themes and give some examples to the user.
Also mention the `feedbackd-device-themes` repository explicitly for users
looking to modify the current `default.json` theme. Adds explanations about the
correct naming of custom theme files and theme file precedence when multiple
themes exist.
Previously, assembly of the theme paths for custom paths (based on
`XDG_DATA_DIRS`) was performed using `g_strconcat`, which produced erroneous
file paths with missing path separators due to a typo in the code.
Instead, make use of `g_build_filename` to assemble the theme paths from
`XDG_DATA_DIRS` to look for custom themes, which automatically introduces
host-specific path separators between individual path components. This
introduces another temporary variable to ensure that the filename (which is
itself assembled from a name and the file ending) isn't mangled by introduction
of a path separator between these two "parts".
Andreas Hartmann