Support Embedding Models with Ollama API

[edubruell]

Description:
Extend the package to support embedding models available through the Ollama API. Allow users to obtain text embeddings for message chains.

Possible Actions:

• Add Embedding Functions: Implement new function ollama_embedding()-function to request embeddings for an llm_message from am embedding model on the Ollama API.
• Data Handling: Ensure that embeddings are returned as numeric vectors or matrices suitable for analysis in R.
• Examples and Use Cases: Include examples in the documentation demonstrating how to use embeddings for different tasks.

[edubruell]

I will do a detailed vignette with the other vignette issue. Version 0.1.4 introduced embeddings that work as expected.