Adds a resource path that will be looked at when looking
for icons, similar to search paths.
This function should be used to make application-specific icons
available as part of the icon theme.
The resources are considered as part of the hicolor icon theme
and must be located in subdirectories that are defined in the
hicolor icon theme, such as `path/16x16/actions/run.png.
Icons that are directly placed in the resource path instead
of a subdirectory are also considered as ultimate fallback.
Adds a resource path that will be looked at when looking for icons, similar to search paths.
This function should be used to make application-specific icons available as part of the icon theme.
The resources are considered as part of the hicolor icon theme and must be located in subdirectories that are defined in the hicolor icon theme, such as `path/16x16/actions/run.png. Icons that are directly placed in the resource path instead of a subdirectory are also considered as ultimate fallback.