write a callback to log images for model errors

[Jeremy Jordan]

What's your idea?
We should log a few example images to Weights and Biases during training so that we can visually inspect model errors.

Describe the solution you'd like
Write a PyTorch Lightning callback that logs images (https://docs.wandb.com/library/log#images-and-overlays) for validation examples that our model is misclassifying.

Note: need to check if we can get model outputs through validation callback metrics.

Parameters:

• Allow users to specify how often this runs (every X epochs)
• Allow users to specify the number of examples to log