This patch creates symlinks (for every application I've
found on Flathub and for which Breeze icon theme has an icon) to let
flatpak-provided .desktop files point to breeze-provided icons.
Flatpak-exported .desktop files use different icon names
(e. g. org.kde.okular instead of just okular) and because of that
flatpak-provided .desktop files show in menus and panels with their
default icons instead of breeze-provided icons even when Breeze icon
theme is used.