Include TeachBooks-Fetch in the documentation and favourites list: add its MANUAL external link to book/_toc.yml and add a favourites entry in book/features/favourites.md so the extension is discoverable from the docs.
Add TeachBooks-Questions to the book TOC and TeachBooks Favourites list, and include Sphinx Gated Directives and TeachBooks Zoomies in the favourites page. Also tidy requirements.txt by removing an inline bump comment from the TeachBooks-Favourites git dependency. Changes touch book/_toc.yml, book/features/favourites.md, and requirements.txt to surface the new/manual links and clean up metadata.
Removed custom bibtex style settings from _config.yml. Added documentation in apa.md about handling duplicate label warnings in APA references, including advice on adding letters to years in .bib files.
Removed local APA style extensions and related static files, updated _config.yml to use the sphinx_apa_references extension, and revised documentation in apa.md to reflect installation and usage of the new package. Added sphinx-apa-references to requirements.txt and references.bib now includes a multi-author example for APA citation demonstration.
Improved the overview and write_online feature documentation by clarifying the description of the TeachBook template and updating its link. Also refined the summary section to specify error reporting per branch and release location.
Added new pages for Sphinx exercise and Sphinx proof extensions, including installation and usage instructions. Updated references, credits, and feature pages to reflect inclusion in TeachBooks Template and Favourites. Improved consistency of external links and badges, and updated submodules to latest versions.
