title: Jenkins render email-ext template to use for other purpose
body: <p>I have an html email template the represents my pipeline result.
  I'm sending the render template by:</p>
  <pre><code>    emailext body: '${SCRIPT, template=&quot;feedback.template&quot;}',
          subject: &quot;Full pipeline details&quot;,
          mimeType: 'text/html',
          to: &quot;${config.to}&quot;
  </code></pre>
  <p>I try to send the rendered html report also via slack by:</p>
  <pre><code>    slackUploadFile filePath: &quot;&lt;MY-rendered-html&gt;&quot;, initialComment:  &quot;Full Report&quot;
  </code></pre>
  <p>I can't figure out how to get the rendered email-template html for other purpose like sending the html via slack or uploading it to somewhere else</p>