- libical-dev for orage
- libgtk-layer-shell-dev for wayland stuff

- This is the new Ubuntu LTS version
- Reorder packages installations
- Install gtksourceview5/gtk4-dev libs
- Bump docker-dind to latest version

- This is needed by autotools when using gettext instead of intltool

- Needed for xfconf distcheck, and might be used in other projects

Add libgtksourceview-4-dev to support mousepad's transition to it.
Also see apps/mousepad!10

- Needed for catfish build

Also take further measures to make the container slimmer and more portable.
Thanks to Romain and Florian (schuellerf/xfce-test)!