LangSmith: Redesigned product homepage and Resource Tags for better organization

The redesigned LangSmith product homepage now focuses on three main areas for building LLM applications: observability, evaluation, and prompt engineering. Observability features include Tracing Projects and Dashboards to help users identify issues and understand their application's performance over time. Evaluation tools consist of Datasets, Experiments, and Annotation Queues to facilitate continuous evaluations and human review processes. Prompt Engineering is supported by prompts storage, versioning, and Playground for real-time prompt iteration. Additionally, improved resource organization with Resource Tags allows users to group resources more flexibly within workspaces.