Addition to shutdown.md

Added section to indicate how to shutdown at a specific time rather than shutting down X minutes from now

pages/linux/shutdown.md

@@ -14,6 +14,10 @@
 
 `shutdown -r +{{5}} &`
 
+- Shutdown at 1:00 pm (Uses 24h clock)
+
+`shutdown -h 13:00`
+
 - Cancel a pending shutdown/reboot operation
 
 `shutdown -c`