feat(helm): add support for spec.ingressClassName to Ingress template

[martinlindner]

Since PR #4437 the helm chart's ingress template generates a kubernetes.io/ingress.class annotation based on .Values.ingress.className for K8s <1.18:

wiki/dev/helm/templates/ingress.yaml

Lines 4 to 8 in de15103

	{{- if and .Values.ingress.className (not (semverCompare ">=1.18-0" .Capabilities.KubeVersion.GitVersion)) }}
	{{- if not (hasKey .Values.ingress.annotations "kubernetes.io/ingress.class") }}
	{{- $_ := set .Values.ingress.annotations "kubernetes.io/ingress.class" .Values.ingress.className}}
	{{- end }}
	{{- end }}

On >=1.18, spec.ingressClassName should be supported instead.

[NGPixel]

Please restore the spaces that were stripped at the end of lines in README.md, these are needed to force a line break in markdown.

[martinlindner]

Oops, sorry, I didn't notice vscode's overly aggressive whitespace trimming.

Should be fixed now, please have another look.