Add image synthesis functionality

[szmazurek]

Is your feature request related to a problem? Please describe. GaNDLF usefulness can be greatly expanded by adding an option to train and use generative networks, such as GANs or diffusion models.

Describe the solution you'd like Generative models and their incorporation into GANDLF framework.

Describe alternatives you've considered Alternatively, user can do generation/augmentation with generative models separately and then use this data from GANDLF. This can be time-consuming and requires extensive knowledge about such models.

Additional context N.A.

[sarthakpati]

Thanks for the report - I have just made some minor edits on the text for consistency. 😄 👍🏽