support for gguf embedding models

[ericcarmi]

Hi, really appreciate the work on this project (the llama-cpp-rs crates are not great).

I would like to load a text embedding model such as: https://huggingface.co/nomic-ai/nomic-embed-text-v1.5-GGUF

I am open to other types of embedding models if nomic is not the right one. Also willing to investigate how to add this myself if I can get some pointers.