Enable using lambdas as Stateless Functional Components

### Problem description

Currently it is not possible to use lambdas as stateless functional components, since they cannot be used as a constructor:

https://github.com/eclipsesource/tabris-js/blob/da6d2595d30d8813b93bc89e4495eb8e29a03cb3/src/tabris/JSX.js#L14

The call to `new` in the example above throws an exception.

### Expected behavior

It should be possible to use lambdas as SFCs. It is easier to declare their signature, they don't bind `this` and are shorter to write.

### Environment

- Tabris.js version: 2.5

### Code snippet

```javascript
import {ui} from 'tabris';

let SimpleSfc = () => ;

ui.contentView.append(

);
```