Using OME-TIFF files generated from FIJI

## Description

When trying to load OME-TIFF files generated from e.g. FIJI, I can't seem to get the VolumeViewer to display the data correctly in the dev server example.

I generated a sample 3-channel 8-bit image stack (200x200x200 pixels) with a single time point, and saved the resultant data using both the "standard" OME-TIFF exporter in FIJI and also using the Bio-Formats exporter plugin.

In both cases, Volume Viewer appears to read the file correctly (three channels show up in the UI drawers) but only the first channel is actually displayed (in purple). I can't seem to get the other channels to display.

I tried this by simply modifying the `index.ts` file to put a URL to my generated file(s) under the `omeTIFF` entry in the `TEST_DATA `map, while keeping the type unchanged (`VolumeFileFormat.TIFF`).

I also tried with a single-channel OME-TIFF file generated in FIJI, and although VolumeViewer appears to load the data and understand that it's a single-channel OME-TIFF file ... I don't see any visual output.

## Expected Behavior

I'd expect all the channel data in the 3- or 1-channel OME-TIFF files to display, as they do for e.g. the `AICS-12_881.ome.tif` file specified in the original test data map.

## Reproduction

Run FIJI and use `File -> New -> Hyperstack`. Specify 8-bit and e.g. 200x200x200 pixels with 3 channels and one "Frames" (i.e., timepoints). Ensure "Label imges" is selected. Then save the resultant data as OME-TIFF via `File -> Save as -> OME-TIFF` or `Plugins -> Bio-Formats -> Bio-formats Exporter`

## Environment

FIJI 1.54f
VolumeViewer 3.8.3 dev (via cloning GitHub repo and `npm dev run`)