Add helper alias in services.yml

[liviucmg]

It would be very useful to add a helper alias in services.yml so that RequireJSHelper can be used inside PHP templates like so:

/* @var Hearsay\RequireJSBundle\Templating\Helper\RequireJSHelper $requireJs */
$requireJs = $view['require_js'];
echo $requireJs->initialize();

Cheers!