feat(gui-v2): add disabled nc-menu-item css

packages/nc-gui-v2/assets/style-v2.scss

@@ -51,6 +51,10 @@ html {
 // menu item styling
 .nc-menu-item {
   @apply cursor-pointer text-xs flex items-center gap-2 px-4 py-3 relative after:(content-[''] absolute top-0 left-0 bottom-0 w-full h-full right-0 bg-current opacity-0 transition transition-opactity duration-100) hover:(after:(opacity-5));
+
+  &.disabled { 
+    @apply text-black text-opacity-25 bg-[#f5f5f5] cursor-not-allowed text-shadow-none box-shadow-none border-[#d9d9d9];
+  }
 }
 
 .nc-sidebar-right-item {