SPA architecture roughly adapted from Jeremy Likness https://blog.jeremylikness.com/blog/build-a-spa-site-with-vanillajs/
URL routing adapted from The Dev Drawer https://dev.to/thedevdrawer/single-page-application-routing-using-hash-or-url-9jh
Github Pages SPA Workaround provided by Rafael Pedicini (see 404.html and github-404-redirect.js for licensure) https://github.com/rafgraph/spa-github-pages