Update docs for file_type of SimpleAnalysis or HS3

[GraemeWatt]

We recently added highlighting of HS3 and SimpleAnalysis resource files in a similar way to HistFactory. See HEPData/hepdata#925 and HEPData/hepdata-submission#16. This PR adds examples of using file_type="HS3" or file_type="SimpleAnalysis" as arguments to sub.add_additional_resource. It also clarifies that analyses should be attached to Submission objects not Table objects. Since changes are only to the docs (and a minor update to a docstring) we don't need a new release of hepdata_lib immediately.

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📚 Documentation preview 📚: https://hepdata-lib--284.org.readthedocs.build/en/284/

[Copilot]

Pull Request Overview

This PR updates documentation and a docstring to reflect newly added support for HS3 and SimpleAnalysis resource file types, which can now be highlighted on HEPData alongside the existing HistFactory support.

Key Changes

• Updated the file_type parameter documentation to include "HS3" and "SimpleAnalysis" options
• Added usage examples for the new file types in the documentation
• Clarified that analysis resources should be attached to Submission objects rather than Table objects

Reviewed Changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated no comments.

File	Description
hepdata_lib/init.py	Updated docstring to document new "HS3" and "SimpleAnalysis" file type options
docs/usage.rst	Added usage examples for new file types, documentation references, and clarification about attaching analyses to Submission objects

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[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 92.21%. Comparing base (96aab5e) to head (1efd5aa).
⚠️ Report is 4 commits behind head on main.

Additional details and impacted files

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##             main     #284   +/-   ##
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  Coverage   92.21%   92.21%           
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  Files           5        5           
  Lines        1118     1118           
  Branches      237      237           
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  Hits         1031     1031           
  Misses         60       60           
  Partials       27       27           

Flag	Coverage Δ
unittests-3.10	90.59% <ø> (ø)
unittests-3.11	90.59% <ø> (ø)
unittests-3.12	90.59% <ø> (ø)
unittests-3.13	90.59% <ø> (ø)
unittests-3.6	90.15% <ø> (ø)
unittests-3.7	90.15% <ø> (ø)
unittests-3.8	91.94% <ø> (ø)
unittests-3.9	90.33% <ø> (ø)

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[clelange]

Looks good to me. I've made sure that the newly added links are working as well.