Inline module scripts can usefully have `async`

[tigt]

https://github.com/csswizardry/ct/blob/1f0a063ceb7eb4dc8f0990d9ff40fb56f7d65006/ct.css#L187-L203

Async and defer simply do not work on inline scripts. It won’t do any harm, but it’s useful to know about.

This is true for classic scripts, but type=module inline scripts can usefully have async applied:

<script type=module>
  // I run like `defer`!
</script>

<script type=module async>
  // I run as soon as encountered but non-blocking!
</script>

defer is still useless, as it is redundant.