Local ncZarr files

[lesserwhirls]

Re: #123 (comment)

The netCDF-C repo currently has seven ncZarr example datasets as part of its testsuite (stored as .zip files):

https://github.com/Unidata/netcdf-c/tree/main/nczarr_test

As @ethanrd discovered, using ncdump on these requires something like:

ncdump -h "file://ref_byte.zarr.zip#mode=nczarr,file,zip