I've published as https://github.com/jmblog/nuxt-netlify-http2-server-push

nuxt-netlify-http2-server-push-module.js

// https://www.netlify.com/blog/2017/07/18/http/2-server-push-on-netlify/

const debug = require('debug')('nuxt:netlify-http2-server-push');
const path = require('path');
const glob = require('glob');
const fs = require('fs');

module.exports = function module(moduleOptions) {
  // This module is only enabled on production builds
  if (this.options.dev) {
    return;
  }
  const hook = builder => {
    debug('Generating a _header file');
    generateHeaderFile(this, moduleOptions);
  };

  this.nuxt.hook('generate:distCopied', hook);
};

const generateHeaderFile = (context, options) => {
  const generateDir = path.resolve(context.options.generate.dir);
  const files = glob.sync(`${generateDir}/**/*.js`);
  let _headers = '/*\n';
  files.forEach(file => {
    _headers += `  Link: <${file.replace(generateDir, '')}>; rel=preload; as=script\n`;
    debug(file.replace(generateDir, ''));
  });
  fs.writeFileSync(`${generateDir}/_headers`, _headers);
  debug('The `_header` file generated');
};

Hey, this is nice thanks!
I have an issue when using it though, cannot compile my nuxt project:

I use it like this in my nuxt.config.js:
modules: [ 'nuxt-netlify-http2-server-push', { // Specify relative path to the dist directory and its content type resources: [ { path: '**/*.js', as: 'script' }, { path: '/img/thomas-morice-logo-black-v2.svg', as: 'image' }, { path: '/fonts/**.*', as: 'fonts' } ] } ],

and here is the error that I have

✖ error nuxt › netlify-http2-server-push › The resources property is required. ✖ fatal TypeError: Cannot read property 'length' of undefined

To fix the error I've mentioned before, you should embed your module and the resources options inside an array in the nuxt.config.js file.