Add support for transformer models

Add a simple example model for detecting defects, both with finetuning and with using embeddings to train a xgboost model

Fixes #39

It would also be nice to support LoRa (or at least add an example on how to use it). https://huggingface.co/blog/Lora-for-sequence-classification-with-Roberta-Llama-Mistral