Add configurable annotations to service

[dannypas00]

This adds configurable annotations to the service. This is sometimes necessary in cloud environments such as google to configure a backendconfig for health checks and other load balancing features:

service:
  type: ClusterIP
  port: 80
  target: 80
  annotations:
    cloud.google.com/backend-config: '{"default": "some-backendconfig"}'
    cloud.google.com/neg: '{"ingress": true}'

[martin-helmich]

LGTM 👍