docs: replace absolute paths by relative

This way, Doxygen also works in GitHub actions

Doxyfile

@@ -61,7 +61,7 @@ PROJECT_BRIEF          = "QML Library for interacting with the Jellyfin multimed
 # pixels and the maximum width should not exceed 200 pixels. Doxygen will copy
 # the logo to the output directory.
 
-PROJECT_LOGO           = /home/chris/Programmeren/Sailfish/harbour-sailfin/sailfish/icons/86x86/harbour-sailfin.png
+PROJECT_LOGO           = sailfish/icons/86x86/harbour-sailfin.png
 
 # With the PROJECT_ICON tag one can specify an icon that is included in the tabs
 # when the HTML document is shown. Doxygen will copy the logo to the output
@@ -74,7 +74,7 @@ PROJECT_ICON           =
 # entered, it will be relative to the location where doxygen was started. If
 # left blank the current directory will be used.
 
-OUTPUT_DIRECTORY       = /home/chris/Programmeren/Sailfish/harbour-sailfin/doxygen
+OUTPUT_DIRECTORY       = doxygen
 
 # If the CREATE_SUBDIRS tag is set to YES then doxygen will create up to 4096
 # sub-directories (in 2 levels) under the output directory of each output format
@@ -949,7 +949,7 @@ WARN_LOGFILE           =
 # spaces. See also FILE_PATTERNS and EXTENSION_MAPPING
 # Note: If this tag is empty the current directory is searched.
 
-INPUT                  = /home/chris/Programmeren/Sailfish/harbour-sailfin/core
+INPUT                  = core
 
 # This tag can be used to specify the character encoding of the source files
 # that doxygen parses. Internally doxygen uses the UTF-8 encoding. Doxygen uses