Support snippets

[Haehnchen]

as having snippets in a clean path structure Foobar/Resources/snippets there are now easily indexable.

{s name=swag-last-registrations/customer-group}{/s}
{s name="frontend/checkout/cart/separate_dispatch" namespace="frontend/listing/box_article"}example text{/s}
...

https://developers.shopware.com/designers-guide/snippets/