Support for NeXus' AXIS_indices attributes

[t20100]

Related to https://github.com/silx-kit/h5web/issues/1446:

According to new NeXus recommendations, AXIS_indices attribute should now be added to NXdata group as a way to properly assign an axis to a signal dimension (rather than relying on the order of the axes attribute). See the example 1. at https://hdf5.gitlab-pages.esrf.fr/nexus/nxdata_axes/classes/base_classes/NXdata.html

We should keep consistent across hdf5/nexus viewer.