Switch to Openbox

Matchbox Window Manager, being designed for mobile devices, does not
handle multiple monitors well.  It manages the monitors together as one
giant screen, which will make it extremely difficult to manage separate
Firefox windows on each screen.  Openbox is almost as lightweight as
Matchbox, but it works significantly better for this use case.

mkrootfs.sh

@@ -22,9 +22,9 @@ dnf --installroot "${destdir}" install -y \
     firefox \
     hostname \
     kmod \
-    matchbox-window-manager \
     mesa-dri-drivers \
     nbd \
+    openbox \
     openssh-server \
     rsyslog \
     systemd \

overlay/home/user/.xinitrc

@@ -4,4 +4,4 @@ xset s off
 xset -dpms
 systemctl --user import-environment DISPLAY
 systemctl --user start graphical.target
-exec matchbox-window-manager -use_titlebar no
+exec openbox