Please add a .gitignore to repository root

[dstults]

Proposed contents of the .gitignore:

__pycache__
OmniGen
tmp

Reasoning:
pycache avoids Python-user-specific binaries from showing up as git drift and prevents their accidentally getting committed
OmniGen is a clone of the HF repo and is used only for caching code and should not get committed either
tmp is for temp files such as loaded images and should not get committed either

[1038lab]

added