Add service annotations to the helm chart

[monneyboi]

When running Aleph in the google cloud with container native loadbalancing, the healthcheck of the default BackendConfig google cloud generates won't work (because of the non-standard name api of the service port if i remember correctly.).

This can be solved in multiple ways:

• I think renaming the port to http would make the defaults work, but i haven't tested this.
• Making it possible for the user to set annotations on the service. Which seems like a good idea anyway.