Add support for ingressClassName (#217)

Hi,

I just add some minor changes to support specifying ingressClassName to support the newer specification in `networking.k8s.io/v1`. The annotation `kubernetes.io/ingress.class: nginx` only works with older API `networking.k8s.io/v1beta1`.

This is part of our move to support kubernetes 1.22.

Co-authored-by: Leong Wai Kit <waikit.leong@bertelsmann.de>
Reviewed-on: https://gitea.com/gitea/helm-chart/pulls/217
Reviewed-by: luhahn <luhahn@noreply.gitea.io>
Reviewed-by: techknowlogick <techknowlogick@gitea.io>
Co-authored-by: wkit23 <wkit23@noreply.gitea.io>
Co-committed-by: wkit23 <wkit23@noreply.gitea.io>

templates/gitea/ingress.yaml

@@ -18,6 +18,9 @@ metadata:
     {{- toYaml . | nindent 4 }}
   {{- end }}
 spec:
+{{- if .Values.ingress.className }}
+  ingressClassName: {{ .Values.ingress.className }}
+{{- end }}
 {{- if .Values.ingress.tls }}
   tls:
   {{- range .Values.ingress.tls }}