feat(render): support JSX fragment

[manucorporat]

JSX fragments allows to have several nodes at the root level without returning an array.
It is now part of the JSX spec, and has some advantages:

return (<>
   <div>node</div>
   {this.condition && <div>now visible</div>}
 </>);

VS

return [
   <div>node</div>,
   this.condition && <div>now visible</div>,
];

Right now, refactoring JSX can be tricky when nodes move from the root to a nested position, JSX fragments makes the syntax for nodes at the top the same as nested nodes.

VS code support since October 2017:
microsoft/TypeScript#19249

[adamdbradley]

Going to close for now until it becomes a larger issue. We'll revisit later.

[NEO97online]

I created an implementation of Fragment for Stencil. It's literally 1 line of code. (52 chars)

https://github.com/michaelauderer/stencil-fragment

@manucorporat This doesn't allow for <> syntax, but still provides the functionality of Fragment for now. It's a default export, so you could import it as F for short, and have <F></F> to work with.

[matthew-dean]

Can this be re-opened? Using fragments is much easier to work with than exporting an array for the same purpose.

[p-vogt]

I'd love to see this beeing added, too. I sometimes find myself using dummy elements (div/span) to avoid using the array notation.