Preloads this link when the user hovers over it.
When the link is clicked later the response will already be cached, making the interaction feel instant.
Preloading a link will enable caching for that link automatically.
Unpoly will only preload links with safe methods.
The number of milliseconds to wait between hovering and preloading. Increasing this will lower the load in your server, but will also make the interaction feel less instant.