Can the script be loaded using the `async` attribute?
The README.md file contains this sample code:

```
<!DOCTYPE html>
<html>
  <head>
    <script src="https://unpkg.com/@phosphor-icons/web"></script>
  </head>
  <body>
    <i class="ph-smiley"></i>
    <i class="ph-fill ph-heart" style="color: hotpink"></i>
    <i class="ph-thin ph-cube"></i>
  </body>
</html>
```

I would like to know if this script will still function as expected if I add an `async` attribute to it, like this:

```
    <script async src="https://unpkg.com/@phosphor-icons/web"></script>
```

This allows the browser to continue rendering the rest of the document even before downloading and executing the script, and it's a recommended practise for web performance.