Add a stub for how to launch lxqt-config-powermanagement

source/3/3.2/3.2.12/power_management.rst

@@ -0,0 +1,8 @@
+Chapter 3.2.12 Power Management
+===============================
+
+Power management manages what to do on laptop batteries when the power is low what happens when your lid to a laptop is closed and what to do when your computer is idle for long periods.
+
+How to Launch
+-------------
+To launch Power Management from the menu -> Prefrences -> LXQt settings -> Power Management. From LXQt configuration center press the power management icon that looks like a light bulb or run lxqt-config-powermanagement from the command line.

source/3/3.2/Prefrences.rst

@@ -15,4 +15,5 @@ Chapter 3.2 Prefrences
   3.2.9/locale
   3.2.10/monitor_settings
   3.2.11/openbox_settings
+  3.2.12/power_management