Add Replicate demo and API

[chenxwh]

Hey @pix2pixzero ! 👋

Really cool work! This pull request makes it possible for people to try your model on the web demo or via API easily. We're using an open-source tool called Cog to make this process easier. View it here: https://replicate.com/cjwbw/pix2pix-zero

Or with Replicate API:

import replicate
model = replicate.models.get("cjwbw/pix2pix-zero")
model.predict(image=...)

We encourage you to try and modify the Replicate page (e.g. Example Gallery) you like, to do so we need to transfer ownership to your account, let me know!

In case you're wondering who I am, I'm from Replicate, where we're trying to make machine learning reproducible. We got frustrated that we couldn't run all the really interesting ML work being done. So, we're going around implementing models we like. 😊