docs: add missing export step in libvirt guide

Signed-off-by: Luca Di Maio <[email protected]>

docs/posts/run_libvirt_in_distrobox.md

@@ -47,6 +47,8 @@ Alternatively, command line:
 ```console
 distrobox create --pull --root --init --unshare-all --image registry.opensuse.org/opensuse/distrobox:latest --name libvirtd --additional-flags "-p 2222:22" \
   --init-hooks "zypper in -y --no-recommends openssh-server patterns-server-kvm_server patterns-server-kvm_tools qemu-arm qemu-ppc qemu-s390x qemu-extra qemu-linux-user && systemctl enable sshd.service && systemctl enable virtqemud.socket virtnetworkd.socket virtstoraged.socket virtnodedevd.socket && usermod -aG libvirt $USER"
+
+distrobox-enter --root libvirtd -- distrobox-export --app virt-manager
 ```
 
 ## Launch from the container