Subscribe to chats callbacks APIs

[https://js.langchain.com/docs/concepts/callbacks/](https://js.langchain.com/docs/concepts/callbacks/)

e.g [https://github.com/getsentry/sentry-python/blob/master/sentry_sdk/integrations/langchain.py](https://github.com/getsentry/sentry-python/blob/master/sentry_sdk/integrations/langchain.py)