Add support for windows

[lbolanos]

This instruction fail in windows
eta install models
/bin/bash: c:userslbolaanaconda3envsfiftyonelibsite-packagesetatensorflowinstall_models.bash: No such file or directory

[blair-ahlquist]

This is an old issue. Is there an official position on it? The fiftyone library should probably just give a "platform not supported" error when trying to load pretrained models (which is how I eventually encountered this issue).