Gotenberg: Add support for service and pod level annotations

[SimonWoidig]

Heyo. I have encountered a missing "feature". I was trying to use the Gotenberg chart and I wanted to take advantage of the prometheus metrics Gotenberg exposes.
So I looked through the values and the chart itself and I found out, that the annotations on pods and/or services cannot be adjusted. This means I cannot use the prometheus.io/scrape: "true" annotation and the others for auto-discovery.
If the annotations could be configured via the values, this issue would be resolved.