Let components receive Observables as props

[kosich]

Currently we allow intrinsic elements to receive Observable attributes, e.g.:

<img src={ of('/bird.png') } /> // > 🦉

Components don't support this feature yet, and passing an Observable to a component results in Component to be of type fn (props$: Observable<{ [key: string]: Observable<…> }>), which leads to boilerplate code. E.g:

<Header title={ of('title') } />

function Header(props: Observable<{ title: Observable<string> }>) {…}

With components it's unclear how exactly the API should look like: props: Observable<{ title: string }> or props: { title: Observable<string> } or a combination of two, or something else.

This issue is a place for further discussions and investigations of this API.