Share our scale factors for making the pointclounds from sdf

[pgarrison]

• Document how to set the scale factor when making pointclounds from SDFs
• Document what scale factor we used

[ritvikvasan]

Scale factor is made available as part of preprocessed data, and there are scripts to compute scale factor. But i think we could add some documentation here

[pgarrison]

@ritvikvasan As far as I can tell, the missing piece is that our documentation for running the preprocessing does not tell users to download the scale_factor.npz file before running the preprocessing (because scale_factor.npz is in the folder with the outputs of the preprocessing).