$ npm install --save @github/details-dialog-element

import '@github/details-dialog-element'

<script type="module" src="./node_modules/@github/details-dialog-element/dist/index.js">

<details>
  <summary>Open dialog</summary>
  <details-dialog>
    Modal content
    <button type="button" data-close-dialog>Close</button>
  </details-dialog>
</details>

<details>
  <summary>Robots</summary>
  <details-dialog src="/robots" preload>
    <include-fragment>Loading…</include-fragment>
  </details-dialog>
</details>

document.addEventListener('details-dialog-close', function(event) {
  if (!confirm('Are you sure?')) {
    event.preventDefault()
  }
})

npm install
npm test