the before option is to insert HTML before the first tag specified -- link in this case.
import { html } from 'ember-apply';
await html.transform(filePath, (tree) => {
  tree.match(({ tag: 'head' }, 'head') => {
    if (node.content) {
      node.content.unshift({ tag: 'noscript', content: 'Please enable javascript' });
    }
    return node;
  });
});
Example borrowed from posthtml-noscript
Generated using TypeDoc
Transform HTML
Uses posthtml for transformation. See: posthtml plugins for examples.