Test for websocket message on creation of resource itself

[timbl]

in https://github.com/solid/test-suite/blob/master/testers/websockets-pubsub/tester/test/surface/change-events.test.ts let us have also another test just the same except the subscription is to the resource which is created, not the container.

see also https://github.com/solid/solid-spec/issues/217