feat: ensure retriever returns an image and send it to the LLM base64 encoded

.changeset/large-plums-drum.md

examples/multimodal/data/1.jpg

examples/multimodal/data/2.jpg

examples/multimodal/data/3.jpg

examples/multimodal/data/San Francisco.txt

examples/multimodal/rag.ts

examples/multimodal/retrieve.ts

packages/core/package.json

packages/core/src/Node.ts

packages/core/src/embeddings/utils.ts

...ages/core/src/indices/vectorStore/VectorIndexRetriever.ts

...es/core/src/synthesizers/MultiModalResponseSynthesizer.ts

pnpm-lock.yaml