Adding implemenatation of From trait to Model for derived signals

[kandrelczyk]

Hi,

I'm trying to do something like that:

let error : RwSignal<Option<SomeError>> = create_rw_signal(None);
let show_error = Signal::derive(move||error.get().is_some()); 

<Modal title="title" show=show_error>
   { display error}
</Modal> 

This didn't work because show has type Model and you can't create Model from derived signal.

I've added the From<Signal<T>> for Model<T> implementation and it's working now.

Is this a good approach? I think especially for components like Modal handling derived signal is very useful but maybe there's better way to do it.

[kandrelczyk]

Closing since it's not needed.