Add example script to switch primary and secondary display applications

also don't run detect-second-display multiple times during a session.

roles/yavdr-desktop/templates/bin/switch-displays.j2

@@ -0,0 +1,9 @@
+#!/bin/bash
+source <(systemctl --user show-environment)
+[[ "$DISPLAY" =~ \.1$ ]] && DISPLAY="${DISPLAY%.1}.0" || DISPLAY="${DISPLAY%.0}.1"
+
+frontend-dbus-send stop
+systemctl --user stop osd2web
+frontend-dbus-send setDisplay "$DISPLAY"
+systemctl --user start osd2web
+frontend-dbus-send start

roles/yavdr-desktop/templates/systemd/user/detect-second-display.service.j2

@@ -3,6 +3,7 @@ Description=Detect second DISPLAY using xrandr
 
 [Service]
 Type=oneshot
+RemainAfterExit=yes
 ExecStart=%h/bin/detect-second-display
 
 [Install]