[FEAT] Support for multi-modal RAG evaluation (including images, tables, etc.)

[joly-chen]

Feature Description
Support for multi-modal RAG evaluation (including images, tables, etc.)

Reason
Multi-modal RAG is becoming more important.

[sfc-gh-jreini]

Hi @joly-chen - multimodal RAG evaluation is already supported. Here's an example notebook you can adapt to your use case: https://github.com/truera/trulens/blob/main/trulens_eval/examples/expositional/models/gemini_multi_modal.ipynb