Sparse Array Support

[Mr-Milk]

Sparse array could be both computational and space-efficient when storing mask images. I wonder if it's possible to support sparse array in NGFF spec.

Just for reference scverse/spatialdata#691

[joshmoore]

Thanks, @Mr-Milk. See also #99.

[Tomatokeftes]

Support for sparse arrays also in general would be extremely useful to be adapted for images with thousands of channels in the field of biomedical imaging. Mass Spectrometry Imaging would greatly benefit from being able to use a NGFF as the current standard imzML format does not scale, and everything else is proprietary vendor formats.