TypeScript Support

LangChain now supports TypeScript, allowing developers to create prompts, chains, and agents natively in TypeScript. Both the Python and TypeScript versions use a serializable format for sharing artifacts between languages. The new package includes all abstractions from the Python version, with plans to expand its ML-centric functionality over time. The TypeScript version of LangChain aims to mirror the Python version as closely as possible, allowing for seamless sharing and prototyping across both languages. Community support has been instrumental in developing this new feature, and feedback and contributions are welcome.