Support and document variable scale factors

[Bisaloo]

Most of the time, we don't want to scale all dimensions in the same fashion. Typically, c is not scaled.

[Artur-man]

ome-zarr-py and spatialdata has a mechanism for that already, we can define a list of named scale vectors with names associated to dimensions:
https://ome-zarr.readthedocs.io/en/stable/api/writer.html#ome_zarr.writer.write_image

we can later use it in spatialdata if we fix the argument as such.

[Bisaloo]

It could be a list of named vectors, or just a list of vectors where the order of elements matches the order in the axes arg

[Artur-man]

Absolutely

[Artur-man]

I have introduced a mechanism for this recently in ImageArray.
https://github.com/BIMSBbioinfo/ImageArray/blob/2daba0bb3deeffb31e93568885785e6345ed221c/tests/testthat/test-imagearray-class.R#L3-L13

Again the concept is similar, or perhaps identical to ome-zarr-py.

See #48 for ome_zarr inheriting from ImageArray class, thus axes specific scaling is performed.