add cert-manager certificate template

common/templates/cert-manager/_certificate.tpl

+{{- define "common.cert-manager.certificate" -}}
+apiVersion: {{ .Values.apiVersion | default "cert-manager.io/v1" }}
+kind: Certificate
+metadata:
+  name: {{ .Values.name | default "certificate" }}
+  {{- with .Values.annotations }}
+  annotations:
+    {{- toYaml . | nindent 4 }}
+  {{- end }}
+  labels:
+    {{- include "common.variables.labels" . | nindent 4 }}
+spec:
+  secretName: {{ .Values.secretName }}
+  {{- with .Values.dnsNames}}
+  dnsNames:
+    {{- toYaml . | nindent 4 }}
+  {{- end }}
+  issuerRef:
+    name: {{ .Values.issuerRef.name }}
+    kind: {{ .Values.issuerRef.kind | default "Issuer" }}
+---
+{{- end }}