devshell: Add deploy-multi command

devshell/commands.nix

@@ -145,5 +145,15 @@ in
       help = "Update installer tag (to trigger new release)";
       command = ''git tag -f installer && git push -f origin installer'';
     }
+    {
+      name = "deploy-multi";
+      category = "tasks";
+      help = "Deploy multiple flakes at once";
+      command = ''
+        for f in $@; do
+          deploy "$O" $f
+        done
+      '';
+    }
   ];
 }