Update renovate.json (#110)

renovate.json

@@ -1,4 +1,12 @@
 {
   "extends": ["config:base"],
-  "enabledManagers": ["cargo", "npm"]
+  "enabledManagers": ["cargo", "npm"],
+  "packageRules": [
+    {
+      "description": "Disable node/pnpm version updates",
+      "matchPackageNames": ["node", "pnpm"],
+      "matchDepTypes": ["engines", "packageManager"],
+      "enabled": false
+    }
+  ]
 }