community/sway: configure xdg-desktop-portal
https://github.com/flatpak/xdg-desktop-portal/issues/1077#issuecomment-1688007044
As explained here, the xdg-desktop-portals loading behavior changed with this 1.17.0. It will no longer fallback to any matching implementation, if no one match the $XDG_CURRENT_DESKTOP value.
This add gtk as default implementation, after wlr.
I used -portalsconf as subpackage to match the phosh recipe.