build: specify packageManager: yarn (#561)

Author: stainless-bot

package.json

@@ -8,6 +8,7 @@
   "type": "commonjs",
   "repository": "github:openai/openai-node",
   "license": "Apache-2.0",
+  "packageManager": "[email protected]",
   "private": false,
   "scripts": {
     "test": "bin/check-test-server && yarn jest",