add support for Velox EMD files containing EELS spectrum images

[PauTorru]

Description of the change

With the new Iliad TFS systems being installed now there are .emd files that contain both EDX and EELS spectrum images. This pull request allows the reader to get the data and metadata of the EELS datasets and create the hspy signals.

Main Changes:

• hs.load("file.emd") loads EELS datasets if present.
• implemented "_read_eels_spectrum_images" on the FeiEMDReader class

Progress of the PR

• Change implemented (can be split into several points),
• update docstring (if appropriate),
• update user guide (if appropriate),
• add a changelog entry in the upcoming_changes folder (see upcoming_changes/README.rst),
• Check formatting of the changelog entry (and eventual user guide changes) in the docs/readthedocs.org:rosettasciio build of this PR (link in github checks)
• add tests,
• ready for review.

Minimal example of the bug fix or the new feature

from rsciio.emd import file_reader
from hyperspy.io import dict2signal

dictionaries = file_reader("file.emd")
signals = [dict2signal(i) for i in dictionaries]

print(any([s.metadata.Signal.signal_type=="EELS" and s.data.ndim>2 for s in signals])) # True

[codecov]

Codecov Report

❌ Patch coverage is 5.26316% with 54 lines in your changes missing coverage. Please review.
✅ Project coverage is 88.52%. Comparing base (06c95ac) to head (3af9675).

Files with missing lines	Patch %	Lines
rsciio/emd/_emd_velox.py	5.26%	53 Missing and 1 partial ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #522      +/-   ##
==========================================
- Coverage   88.88%   88.52%   -0.37%     
==========================================
  Files         113      113              
  Lines       13045    13102      +57     
  Branches     2414     2425      +11     
==========================================
+ Hits        11595    11598       +3     
- Misses        910      963      +53     
- Partials      540      541       +1     

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[ericpre]

From a quick look, it looks good. It would need some test files - see guidelines in https://hyperspy.org/rosettasciio/contributing.html#making-test-data-files.

[PauTorru]

pre-commit.ci autofix

[PauTorru]

Looks like Eduardo beat me to it in PR #524