Proposal: MountApp component

## Currently

We use `getMountableComponent(app)` function, to get a component which has the `app` inside React's context.

## Proposal

We can have a `MountApp` component, with usage like:

```js
import { MountApp } from 'frint-react';

const fooApp; // instance

function BarComponent() {
// render a given app with instance
return ;

// render a given app by name
return

// render any component against an app
return }
/>;
}
```

## Further usage

In `frint-react`: The `MountApp` component can then be used by `Region` component and `render` function internally too.

`getMountableComponent` can be deprecated.

## Benefits

We don't have to depend on placing a Region with a name to mount an app somewhere. We can benefit from directly rendering an App somewhere without expecting any other App to share that region.