feat: Gemini Access via Vertex AI (#838)

.changeset/fuzzy-coins-breathe.md

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

examples/gemini/chatVertex.ts

packages/autotool/examples/02_nextjs/next.config.mjs

packages/core/package.json

packages/core/src/embeddings/GeminiEmbedding.ts

packages/core/src/index.ts

packages/core/src/llm/gemini/base.ts

packages/core/src/llm/gemini/types.ts

packages/core/src/llm/gemini/utils.ts

packages/core/src/llm/gemini/vertex.ts

packages/core/src/llm/index.ts

packages/core/src/llm/utils.ts

packages/core/src/next.ts

pnpm-lock.yaml