This is version of the accessibility checker, exported from Observable (https://observablehq.com/@jtrim-ons/xlsx-accessibility-checker).
It can be run on a local web server, and is also available on GitHub Pages.
I've tweaked index.html. I also re-ordered some of the cells to put the styles early and named a cell "start_of_appendix".
I've edited runtime.js to get scripts from lib/ rather than the jsdelivr service.