Add an #[embedded_css_module] macro for non dx-serve/dx-bundle enviorments.

## Feature Request
the static type checking that `#[css_module]` macro has is very useful, but it's locked behind `dx serve`/`dx bundle`. If you are using dioxus in an environment where you don't have access to those (bevy dioxus native), (side-stepping the bundler for direct executable files), you can't use it. `Asset!` does work for these environments, but you lose #[css_module]'s type checking.

If there were a `#[embedded_css_module]`, it would allow keeping css classes type checked while still being able to work in non `dx serve`/`dx bundle`-able environments.