Support for Link Prefetching

Hey there,

I was thinking about how to speed up navigation and remembered the case where some flickr pictures were getting deleted because some browsers where prefetching links. But, flickr had implemented `DELETE` as `GET`… ¬_¬ lovely!

Anyway, these days HTML supports adding `prefetch` (and the likes) hints to the browser so it speeds up certain aspects of the navigation.

As part of that, there's also lazy loading images (which could be its own separate GH issue)… A quick search in this repository gave me a couple of hints that the library we're using to render images already support it (?).

The issue identifies HTML prefetch hints and possible lazy-loading support in the image-rendering library, but names no files or tests. Start by locating the navigation and image-rendering entry points, then determine the intended supported behavior and how it can be verified.

Written by the indexing model from the issue text.