Defines the "preload" keyword that may be used with `link` elements or Link header. This keyword provides a declarative fetch primitive that initiates an early fetch and separates fetching from resource execution.
Docs: https://www.smashingmagazine.com/2016/02/preload-what-is-it-good-for/ https://developers.google.com/web/updates/2016/03/link-rel-preload