feat: init gemini llm (#769)

.changeset/light-ears-begin.md

...cs/docs/modules/embeddings/available_embeddings/gemini.md

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

examples/gemini.ts

examples/gemini/chat.ts

packages/core/package.json

packages/core/src/embeddings/GeminiEmbedding.ts

packages/core/src/embeddings/index.ts

packages/core/src/llm/gemini.ts

packages/core/src/llm/index.ts

packages/edge/package.json

pnpm-lock.yaml