chore: add .superstack/ to gitignore

Author: Anmol1696

.gitignore

@@ -140,7 +140,9 @@ vite.config.ts.timestamp-*
 
 # Generated function workspace packages (created by scripts/generate.ts)
 generated/
-
 # Rendered Kubernetes manifests may include Secret objects. Regenerate locally
 # with k8s/Makefile targets instead of committing them.
 k8s/manifests/*.yaml
+
+# Superstack scratch
+.superstack/