[FEAT] Expose default slot as prop

[cossssmin]

Would be useful to be able to get the content passed to a component as a prop, i.e.:

// button.html
<script props>
  module.exports = {
    yield: $slots.default // or props.yield maybe?
  }
</script>

<!--[if mso]>
  <a href="...">{{ yield }}</a>
<![endif]-->
<a href="..." style="mso-hide: all">
  <yield />
</a>

This way we could render the <yield /> tag in HTML comments where it doesn't render normally, through a prop.

Yes it can be passed like a prop but tbh this looks stupid to me, plus it's cumbersome to pass HTML as the label:

<x-button href="..." label="Hello World">
  Hello World
</x-button>