code: function generateTemplate(context) {
    let _page;
    let _phantom;
    phantom.create([], { logLevel: 'error' }).then(function (ph) {
      _phantom = ph;
      ph.createPage()
        .then(page => {
          _page = page;
          const url = path.join(context.config.destRoot, context.sample.embed);
          return _page.property('viewportSize', {width: 1024, height: 768})
            .then(() => _page.open(url) );
        })
        .then(status => {
          return _page.evaluate(function() {
            const element = document.querySelector('#source-panel');
            const height = element.getBoundingClientRect().top + element.offsetHeight;
            return height;
          });
        })
        .then(height => {
          context.sample.height = height;
          generate(context.sample.template, templates.template, context);
        })
        .then(() => {
          _page.close();
          _phantom.exit();
        })
        .catch(err => console.log(err));
    });
  }
docs: Opens the embed html file in a browser to determine the initial height.