24_vision.gan: create docments

[marii-moe]

Add documents to 24_vision.gan.

See the style guide and contribution guide for more details (links will be added when created).

This requires a beginner familiarity with fastai such as callbacks, but does require specialized understanding of GANs. This notebook defines how to automatically create a GANLearner, including both generator and critic, as well as a few methods for switching between them.

Documents progress(only one section:

• [ ] Wrapping the modules
• [ ] Callbacks for GAN training
• [ ] GAN data
• [ ] GAN Learner

[tmabraham]

I'll assign this one to myself...