Make websockets available in devcontainer

[oweitman]

Description:
Without this change the devcontainer cant work, because websocket requests dont target /socket.io/ location.

[AlCalzone]

@UncleSamSwiss I think this is one for you

[oweitman]

1. i tested the changes directly on an running test environment.
2. another change i did not include in the PR was: i must remove the following command from postCreateCommand, because it fails, but i dont know why. i dont care if the dicovery adapter is in the dev environment, or i can remove by my self iob del discovery &&
3. i am able do change and debug the adapter in vs code
4. i dont have tested dev in the admin/react section
5. i tried to test the complete lifecycle with starting the create-adapter script from my fork with npx oweitman/create-adapter it downloads, but didnt start without an error message