Add Replicate demo and API

[chenxwh]

Impressive model!

This pull request makes it possible to run shap-e on Replicate (https://replicate.com/cjwbw/shap-e) and via API:

import replicate
model = replicate.models.get(<model_name>)
model.predict(prompt=...)

We would also like to transfer the ownership to openai so you could easily modify the model and push changes :)