add [h5,nc]ndims. [h5,nc]size scalar is empty. h5save write scalar size accurately

• add functions "h5ndims" and "ncndims" to get rank of disk variables
• "h5size" and "ncsize" return empty [] if disk variable is scalar. This is like Python etc.
• "h5save" better respects optional "size" argument to optionally write scalars instead as 1 or more dimensions e.g. [1,1,1]. This is necessary to interface with other languages.

[sha256,md5]sum return string, add mac/windows CI

CI for Matlab now has MacOS, Linux and Windows

improve [sha256,md5]sum by outputting string instead of char, as typical use case is == check.

absolute_path UX, improve test coverage

absolute_path: return UNC paths unmodified, print invalid path if canonicalize fails

add subprocess_run test of env=

test fileio.which: accommodate Matlab on MacOS

use CMake to extract zstd

Most of our users will have CMake already, at least as likely as having zstd without having to use an intermediate temporary file. So it's faster and robust.

improve test coverage, cleanup lint

Improve auto-linter, resolve minor issues thereby discovered

which: streamline logic

allow fpath to be a scalar or array

[h5,nc]save: allow bare filename

[h5,nc]save: allow plain filename without folder

ci: update actions

HDF5 scalar write, Matlab >= R2020b

Matlab doesn't have a high-level function to write scalar HDF5 dataset, so we added it to our h5save.

To avoid excess code, we put enhanced argument checks in stdlib.hdf5nc functions that require Matlab >= R2020b.

add fileio.sha256sum

v4.0.1

add fileio.sha256sum

reorganized as stdlib

combined a few complimentary libraries into this stdlib.

import hdf5nc.* => import stdlib.hdf5nc.*