[PHPStorm] Support goto for theme templates

[lolautruche]

Themes feature introduce an @ezdesign special Twig namespace. By default this namespace is not recognized by PHPStorm Symfony plugin because it's a virtual namespace.

Solution would be to generate a ide-twig.json file using format supported by Symfony plugin (supported since v0.11.110)

Format must be:

{
  "namespaces": [
    {
      "namespace": "foo",
      "path": "some/relative/path"
    }
  ]
}