✨ (flatpak-sync) Add usage command printing the help

flatpak-sync/flatpak-sync.sh

@@ -24,10 +24,11 @@ error() {
 }
 
 usage() {
-    info "Usage: flatpak-sync [sync | add <appId> | remove <appId> ]"
+    info "Usage: flatpak-sync [sync | add <appId> | remove <appId> | usage]"
     info "sync: Synchronized installed apps with app list."
     info "add | a | install | i: Add app with app id to the list and sync."
     info "remove | r | uninstall | u: Remove app with app id from the list and sync."
+    info "usage: Print this help."
     info "Without any given argument a sync is executed."
 }
 
@@ -128,6 +129,9 @@ case "$cmd" in
         remove "$@"
         sync
         ;;
+    usage )
+        usage
+        ;;
     * )
         sync
 esac