i3: Add 'power' mode binding

This adds a seperate mode binding for controlling power state (suspend,
reboot and poweroff)

i3/.config/i3/config

@@ -208,12 +208,28 @@ bindsym XF86AudioRaiseVolume exec --no-startup-id pactl set-sink-volume @DEFAULT
 bindsym XF86AudioLowerVolume exec --no-startup-id pactl set-sink-volume @DEFAULT_SINK@ -5%
 bindsym XF86AudioMute exec --no-startup-id pactl set-sink-mute @DEFAULT_SINK@ toggle
 
-# Lock and power settings
+# power settings
+set $mode_power Power: [s]uspend [r]eboot [p]oweroff
+mode "$mode_power" {
+	# These bindings trigger as soon as you enter the power mode
+
+        # Pressing r will reboot
+        # Pressing p will poweroff
+        # Pressing s will leave power binding mode and suspend
+        bindsym r exec --no-startup-id systemctl reboot
+        bindsym p exec --no-startup-id systemctl poweroff
+        bindsym s exec --no-startup-id i3-msg mode "default" && systemctl suspend
+
+        # back to normal: Enter or Escape
+        bindsym Return mode "default"
+        bindsym Escape mode "default"
+}
+
+bindsym $mod+p mode "$mode_power"
+
+# lock settings
 exec --no-startup-id light-locker --lock-on-suspend
 bindsym $mod+u exec --no-startup-id light-locker-command -l
-bindsym $mod+i exec --no-startup-id systemctl suspend
-bindsym $mod+p exec --no-startup-id systemctl poweroff
-bindsym $mod+z exec --no-startup-id systemctl reboot
 
 # Brightness
 bindsym XF86MonBrightnessDown exec --no-startup-id brightness decrease 50