Add fMoW dataset

[adamjstewart]

Summary

Let's add a data loader for the Functional Map of the World (fMoW) dataset.

Rationale

I don't normally open issues for adding dataset XXX, but someone asks me about this specific dataset at least once a month, so let's finally do it.

Implementation

There are a few different versions of the dataset worth adding:

• fMoW-rgb, fMoW-full: https://github.com/fMoW/dataset
• fMoW-Sentinel: https://purl.stanford.edu/vg497cb6002
• @isaaccorley was working on a Landsat version?

Alternatives

No response

Additional information

No response

[isaaccorley]

I have Landsat versions of EuroSAT, BigEarthNet, and fMoW just need to upload to HF and finish writing up this short paper about it.