Support flipped-y images (origin at the bottom left, not top left)

[kylebarron]

To unblock #261 because the raw AEF GeoTIFFs were exported upside down.

@gadomski put a test image in geotiff-test-data https://github.com/developmentseed/geotiff-test-data/blob/main/real_data/source-coop-alpha-earth/xjejfvrbm1fbu1ecw-0000000000-0000008192_info.md