Add Replicate demo and API

[chenxwh]

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Hi @zRzRzRzRzRzRzR,

Great work on CogVideoX!

This pull request makes it possible to run CogVideoX on Replicate (https://replicate.com/chenxwh/cogvideox-t2v, https://replicate.com/chenxwh/cogvideox-i2v). Also we'd like to transfer the demo pages to THUDM so you can make modifications easily, and happy to help maintain/integrate the upcoming changes and improving the demo :)