Micro-UI support/example

[tracker1]

Would be nice to have an example, where the mounting point(s) are passed in from javascript, as well as returning access points for say setting state.

From JS side, similar to the two apps example:

import { ComponentName } from 'outputFromYewProject`;

const component = new Component(document.querySelector('.first-app'));
component.foo('some value');
component.onBar((v1, v2) => console.log{{v1, v2});
console.log(component.baz());

This could then be used to develop micro-ui based on yew, but able to create micro-ui to transition portions of applications, or have yew based apps that are embedded into other components. I think the above, as an example would be enough of a starting point..

About the only thing that might be nice to add, would maybe be some sort of means of sharing state access for something similar to Redux, but as a separate wasm that's passed into the micro-ui component instance, but I don't think that's really possible just yet.