Update documentation to reflect running this on a Cloud instance.

[mcam10]

This should include:

1. Creating an ssh keypair for the instance saving inside of the users Github Profile. In order to properly checkout the code via:
   git clone --recurse-submodules [email protected]:replicate/flux-fine-tuner.git

2. Cog build

3. Cog train -i input_images=@${path_to_local_images}.zip

[mcam10]

I can also take this if this would be helpful for the community to have :).