Provide an example Zarr file and use it in examples

[abhibaruah]

CR feedback:
Should we provide some example/test files as part of the repo? That way people can try things out immediately and these examples can use those files...

[Ajaxels]

That's always a good idea, as it makes examples run smoothly. If you want, I can send you some volume electron microscopy example that I am typically using for training.