`docs/` is served as its own GitHub Pages project site (verified live:
`codecheck.org.uk/register/<anything>` returns GitHub's stock 404 today,
not the parent `codecheck.org.uk` site's Jekyll one), so a `docs/404.html`
here is what every missing path under `/register/` gets shown.
Usage
generate_404_page(output_dir = "docs")
Arguments
- output_dir
Output directory (default: "docs")
Value
Invisibly returns the path to the generated 404.html
Details
Reuses [generate_navigation_header()] for the nav bar - the same markup
every other page's prefix uses - rather than duplicating it; there is no
pandoc render step here, this is a small hand-built page like a
codechecker/person redirect stub.