Implemented a requested feature to keep <details> sidebar menu
elements expanded when on that page. Much more difficult than it would
seem. The sidebar menu is just Markdown so couldn't be done with HTML.
Not possible with CSS. Want to keep the site free from JavaScript.
The solution
was to post-process the sidebar HTML with Mojo::DOM, find any
<a[href=$slug]> elements, then iterate up over their ancestors for
any <details> elements and add the open tag. Also I put on a
selected class to allow styling the actual selected link.
Implemented smart typography. "So now I'm able --- to do this!" I love how little code this was. I thought it would be difficult. My main win was using the preexisting recursion counter to only parse the Mojo::DOM at the top-level loop.