ingressClassName field missing

[ciechonp]

As of Kubernetes 1.18 ingressClassName field was added. kubernetes.io/ingress.class is now deprecated.
https://kubernetes.io/docs/concepts/services-networking/ingress/#deprecated-annotation
Can Ingress definition in this chart be updated to include ingressClassName field?

[arm4b]

Thanks for the report 👍
A PR contribution would be helpful to support this.

[arm4b]

somewhat related to #331