add web component support by adding :host to the output

[itsmebasti]

I am using some tw classes in my lit web components.
I use the cli to create a css file and then load it to the affected web components.
With tw4 it stopped working due to the new theme layer not being applied to :host elements, but only :root elements.
If :host it added to the output the solution works again.

/*! tailwindcss v4.0.0 | MIT License | https://tailwindcss.com */
@layer theme, base, components, utilities;
@layer theme {
  :root, :host {
    --font-sans: ui-sans-serif, system-ui, sans-serif, "Apple Color Emoji",