Add Replicate demo and API

[chenxwh]

trafficstars

Hey @tianweiy, @Guangxuan-Xiao! 👋

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

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

We would also like to transfer the ownership to mit-han-lab so you could easily modify the model and push changes :)