Commented out the code related to the 'sphinx_gated_directives_registry' in favor of using only the 'sphinx_gated_directives_super_registry'. Updated purge and transform logic accordingly. Added clarifying comments to code-align.css regarding left alignment enforcement.
Introduces the custom Sphinx extension 'sphinx_gated_directives' for start/end directive gating and validation, registering it in the Sphinx local extensions. Also adds a CSS file to enforce left alignment for code cells. Updates _config.yml to configure the new extension and set the documentation language to English.
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.
