Add an option to annotate services

[cgehrmann]

Add an option to add annotations to service via the value.yaml file.

This would enable services like external-dns to do their work and create DNS entries.

Similar to: Add an option to annotate and labels seq pods #9

[nblumhardt]

Thanks for the suggestion. I think we're open to both of these, if anyone's interested in sketching out a PR 👍