static getRelationsFromNode(node) {
    if (
      node.nodeType === node.ELEMENT_NODE &&
      node.matches('link[href][rel~=preload]')
    ) {
      return {
        type: 'HtmlPreloadLink',
        from: this,
        to: {
          url: node.getAttribute('href'),
          contentType: node.getAttribute('type') || undefined,
        },
        as: node.getAttribute('as') || undefined,
        node,
      };
    }
  }
@extends {HtmlResourceHint}

Implementation of http://w3c.github.io/preload/#dfn-preload