Handle `label` data in OME-Zarr

## Use Case

Max was trying to visualize an OME-Zarr in TFE that has a nested `labels` group, which contains segmentations. Segmentations/labels have the same dimensions as the original Zarr image, but there can be multiple of them.

The structure looks like this:
- `data.zarr`
- .zattrs
- .zgroup
- 0
- 1
- 2
- ...
- `labels`
- `cell`
- .zattrs
- 0
- 1
- 2
- ...
- `nuclei`
- .zattrs
- 0
- 1
- ...

I'm trying to find the exact spec, but he mentioned that he's following the `v0.4` spec.
https://ome-zarr.readthedocs.io/en/stable/python.html#writing-labels

It would be great if we could visualize these in Vol-E! Maybe as additional channels?

## Solution

_Please describe your ideal solution_

## Alternatives

_Please describe any alternatives you've considered, even if you've dismissed them_