Create a fine-tuning notebook and utilize pre-trained models

[lurauch]

We should add a notebook where we show how to

1. utilize a pre-trained model (with pretrained datamodule)
2. utilize these models for fine-tuning (embedding model and full fine-tuning)
3. should be implemented in DT

I think we need two tutorials for this:

1. Fully integrated into this workflow
2. External workflow in external code (BirdSet can be installed externally and can then be used for data preparation and model loading)