swaync-service-dispatcher: add a usage command

hosts/common/programs/swaynotificationcenter/swaync-service-dispatcher

@@ -5,6 +5,17 @@
 # otherwise we invoke a s6-rc which does not know where to find files.
 export PATH="/etc/profiles/per-user/$(whoami)/bin:/run/current-system/sw/bin:$PATH"
 
+usage() {
+  echo "swaync-service-dispatcher <action> <service>"
+  echo ""
+  echo "actions:"
+  echo "- swaync-service-dispatcher print <service>"
+  echo "  - prints 'true' or 'false' based on if the service is wanted-up (i.e. started or starting)"
+  echo "- swaync-service-dispatcher toggle <service>"
+  echo "  - if the service is up, takes it down, and vice versa"
+  exit 1
+}
+
 action="$1"
 service="$2"
 
@@ -34,10 +45,10 @@ stopService() {
 }
 
 case "$action" in
-  print)
+  (print)
     checkActive
     ;;
-  toggle)
+  (toggle)
     case "$(checkActive)" in
       false)
         startService
@@ -47,4 +58,7 @@ case "$action" in
         ;;
     esac
     ;;
+  (*)
+    usage
+    ;;
 esac