Add support for custom deployment annotations to Helm chart

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Is your feature request related to a problem? Please describe.

I need to add some annotations to the deployment resource in order to use CircleCI Releases. Unfortunately the Router Helm chart does not provide this as a config option. Although my use case is quite specific I believe it's a fairly common requirement for people to need to add custom annotations to deployments.

This is already supported for deployment/pod labels via extraLabels and for pod annotations via podAnnotations but there is no support for deployment annotations.

Describe the solution you'd like

I'd like the same approach already used to support pod annotation but for deployments.

Example: deployment.yaml

{{- if .Values.deploymentAnnotations }}
{{- toYaml .Values.deploymentAnnotations | nindent 4 }}
{{- end }}

Describe alternatives you've considered

Not sure how else to achieve this without forking the Helm chart

Additional context

CircleCI Releases Doc: https://circleci.com/docs/release/configure-your-kubernetes-components/