Announcing LangChain Hub

LangChain Hub is a new platform for uploading, browsing, pulling, and managing prompts. It's integrated into LangSmith and offers read and write permissions depending on access level. The motivation behind the hub is to make it easier to share and discover prompts across various use-cases and industries. The goal is for LangChain Hub to become the go-to place for developers to discover new use cases and polished prompts. Currently, only prompt templates are supported, but plans include adding support for other artifact types like chains and agents.