Updating Appendix A for new formats

[VisLab]

This will need several PRs to update fully.

[Copilot]

Pull request overview

This pull request updates Appendix A of the HED specification to document new schema formats (JSON and TSV), while also modernizing the project dependencies and reorganizing the documentation structure. The changes support the evolution of the HED ecosystem by providing comprehensive documentation for the newer schema file formats introduced in version 8.5.0.

Changes:

• Added comprehensive documentation for JSON and TSV schema formats in Appendix A
• Updated schema version references from 8.0.0/8.4.0 to 8.5.0 throughout Appendix A
• Modernized Python development dependencies (Sphinx, Furo, Black, Ruff, mdformat)
• Restructured documentation index with clearer sectioning (Core specification, Advanced topics, Reference materials)

Reviewed changes

Copilot reviewed 4 out of 4 changed files in this pull request and generated 3 comments.

File	Description
pyproject.toml	Consolidated dev dependencies, removed separate docs/quality groups, updated package versions
docs/source/index.rst	Reorganized table of contents into logical sections with separate toctrees
docs/source/conf.py	Added keyboard navigation support for Furo theme
docs/source/Appendix_A.md	Updated schema version to 8.5.0, updated unit class tables, added detailed JSON format section (A.4), added comprehensive TSV format section (A.5), expanded attribute descriptions

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