docs: add available LLMs (#536)

apps/docs/docs/modules/llms/_category_.yml

apps/docs/docs/modules/llms/available_llms/_category_.yml

apps/docs/docs/modules/llms/available_llms/anthropic.md

apps/docs/docs/modules/llms/available_llms/azure.md

apps/docs/docs/modules/llms/available_llms/llama2.md

apps/docs/docs/modules/llms/available_llms/mistral.md

apps/docs/docs/modules/llms/available_llms/ollama.md

apps/docs/docs/modules/llms/available_llms/openai.md

apps/docs/docs/modules/llms/available_llms/portkey.md

apps/docs/docs/modules/llms/available_llms/together.md

apps/docs/docs/modules/llms/index.md

examples/anthropic.ts