feat: support anthropic and gemini model providers and update to LITS 0.3.3 (#63)

...es/types/streaming/nextjs/app/api/chat/engine/settings.ts

.../types/streaming/nextjs/app/api/chat/llamaindex-stream.ts

templates/types/streaming/nextjs/app/api/chat/route.ts

templates/types/streaming/nextjs/package.json