docs: modernize README with tables, fenced code blocks, and admonitions

replaced __init__.py with gitignore

Removed debug asserts from loss.py

commit demo-images dir

newlines in readme

Removed contents of demo. updated readme and architecture image

I'm an idiot; loss was perfectly fine.

Per pixel cross entropy should have had logits=True, bc no softmax was

made gitignore remove demo images, keep weights dir. todo: update poster

added reference to Fu et al. paper

increased readme image size

added assets, download script does encoder model now too

updated readme

updated readme

removed extra ImageDataGenerator line in predict.py.