Converting ONNX file into Axon

[meanderingstream]

The notebook presents an approach to using axon_onnx to parse an ONNX model into an Axon model.

The notebook could be moved to axon_onnx, however, I think it belongs with the Axon library to demonstrate turning ONNX models into Axon models.

[meanderingstream]

Changed the onnx_to_axon notebook to have a realistic representation of converting a custom model saved in ONNX into Axon. Demonstrated how to run inference on multiple images. Used small cells that allow the user to explore how the data changes from the functions in the cell. Included links to the source ONNX models on huggingface and source images used in training the original model.