Add zarr.js

[manzt]

#19 @joshmoore @jakirkham

This PR adds a node-js based zarr writer for zarr.js. An important note is that due to the many runtime environments for JavaScript, there is no default FSStore in Zarr.js. This is because each runtime environment (e.g. node, deno, and web-browsers) provide different APIs for interfacing with the file system. Zarr.js doesn't rely on any platform specific APIs, which makes it more portable as a library, but I had to add a minimal FSStore implementation to this repo to enable writing to disk.

As a side note, I found the ergonomics of the zarr.js API for creating stores to not be very user friendly. This is probably because zarr.js use-cases are almost entirely read-only in the web-browser. It is probably ideal to add zarr.js as a reader (in a browser environment), but I'm not sure what steps to take in that direction given the pytest env.

[manzt]

Tests are passing for zarr reader but not z5py...

E       RuntimeError: [json.exception.type_error.302] type must be number, but is null

I think this has something to do with the default fill_value in zarr.js. Not sure when I'll have time to explore further.

[joshmoore]

test/test_read_all.py::test_correct_read[read js zarr using z5py, blosc] PASSED [  2%]
test/test_read_all.py::test_correct_read[read js zarr using z5py, gzip] PASSED [  4%]
test/test_read_all.py::test_correct_read[read js zarr using z5py, raw] PASSED [  6%]
test/test_read_all.py::test_correct_read[read js zarr using z5py, zlib] PASSED [  8%]
test/test_read_all.py::test_correct_read[read js zarr using zarr, blosc] PASSED [ 10%]
test/test_read_all.py::test_correct_read[read js zarr using zarr, gzip] PASSED [ 12%]
test/test_read_all.py::test_correct_read[read js zarr using zarr, raw] PASSED [ 14%]
test/test_read_all.py::test_correct_read[read js zarr using zarr, zlib] PASSED [ 16%]

Very good stuff! I notice things aren't really set up for reading with non-Python languages. Happy to get this merged while some thought is put into that.

[constantinpape]

@manzt looks great! I think this is good to be merged, any objections?

@joshmoore

Very good stuff! I notice things aren't really set up for reading with non-Python languages.

Indeed, we should add read tests for other languages.

[manzt]

No objections on my end!