Date-stamp in page footer?

Having the last changed date from the source `wiki/Example.md` file in the HTML rendered version would be useful for readers. I've seen an example putting the site rendering time-stamp in the footer, but that is less useful.

Start by tracing how wiki/Example.md is rendered into HTML and where the page footer is assembled. Confirm how the source file's last-changed date can be exposed, then verify that the rendered page shows that date rather than the site render time.

Written by the indexing model from the issue text.