main/postmarketos-ui-phosh: add xdg-desktop-portal-wlr

Since it's the recommended for the screencast feature https://gitlab.gnome.org/World/Phosh/phosh/-/merge_requests/1301

This in a way depends on pipewire: https://gitlab.alpinelinux.org/alpine/aports/-/merge_requests/50236

So I'm not totally sure that this is safe. Even though when I installed it, pipewire-pulse did not actually got installed, so maybe it's safe? This needs testing, and I don't really make use of the feature. @adamthiede do you have any way to test this? EDIT: ASHPD Demo works, so should actually do work :D