State does not persist when xarray dimension name is a not valid Neuroglancer dimension name

I have Zarr data generated via [xarray.Dataarray.to_zarr](https://docs.xarray.dev/en/stable/generated/xarray.DataArray.to_zarr.html). This includes the units in brackets: `"xpix [µm]"`.

While Neuroglancer can view this data initially, it seems unable to serialize this state properly in the URL. Refreshing, sharing the URL from the address bar, or copying the JSON state fails to reproduce the state.

After testing I determined that Neuroglancer considers both the brackets and the `µ` as illegal characters.

```json
{
"shape": [
5370,
9,
180,
180
],
"data_type": "int16",
"chunk_grid": {
"name": "regular",
"configuration": {
"chunk_shape": [
32,
9,
45,
45
]
}
},
"chunk_key_encoding": {
"name": "default",
"configuration": {
"separator": "/"
}
},
"fill_value": 0,
"codecs": [
{
"name": "bytes",
"configuration": {
"endian": "little"
}
},
{
"name": "zstd",
"configuration": {
"level": 0,
"checksum": false
}
}
],
"attributes": {},
"dimension_names": [
"volumes [s]",
"planes [µm]",
"xpix [µm]",
"ypix [µm]"
],
"zarr_format": 3,
"node_type": "array",
"storage_transformers": []
}
```