Features: Support saliency method: Grad-CAM

[seoulsky-field]

What

• Add a function which shows the saliency maps.
• First, we support Grad-CAM because it's a representative method.
• Save saliency maps with wandb option.

Why

• From the perspective of aid to medical doctors, nowadays, Grad-CAM is one of the most used methods.
• Even though, unfortunately, it's not a verified method in medical task from the perspective of XAI in deep-learning, many corporations still use saliency maps for medical doctors. So, I determined to provide saliency maps for users who are the medical doctors and researchers.
• Among the lots of saliency methods, I chose Grad-CAM first by referring to the paper "Benchmarking saliency methods for chest X-ray interpretation".

How

• Implement to support Grad-CAM.
• Save saliency maps in local.
• Save saliency maps in wandb.