HTTP Strict-Transport-Security / How or where can I can I add the header?
Hi, 

We use ratchet with TLS as websocket server (wss://) and so far it works very well. However, after a security screening we were told that it would be a good idea to use HTTP Strict-Transport-Security also for websockets. 

Basically we would like to add the following header:

```php
header("Strict-Transport-Security: max-age=63072000; includeSubDomains; preload");
```

Where could this happen?

Thanks.