first-run: Add needed OpenSuse packages needed to install dolphin.

This lets me locally get through a Docker image that starts from stock
opensuse/leap:15.0 and then does only (with kdesrc-build volume-mounted
into the running container):

kdesrc-build --initial-setup
kdesrc-build --include-dependencies --stop-on-failure dolphin

I haven't tried running it yet but this would be a good baseline to
continue with per-app dependent non-KDE packages.