Polybar: Add module to show pending reboots

.config/polybar/config

@@ -73,7 +73,7 @@ modules-right = fshome | wlan-laptop wlan-desktop
 monitor = ${env:PB_MONITOR:eDP-1}
 inherit = template/bar
 border-top-size = ${res/config.border-size}
-modules-left = battery cpu memory
+modules-left = battery cpu memory reboot-required
 modules-right = backlight pulse | date
 
 [bar/secondary]
@@ -243,6 +243,12 @@ bar-volume-empty = ${res/config.bar-empty}
 bar-volume-empty-foreground = ${res/colors.gray}
 bar-volume-indicator = ${res/config.bar-indicator}
 
+[module/reboot-required]
+type = custom/script
+exec = "echo Reboot required"
+exec-if = "[ -f /var/run/reboot-required ]"
+format-foreground = ${res/colors.yellow}
+
 [module/wlan-laptop]
 type = internal/network
 interface = wlp1s0