Improving DRY principle support on gitea Ingress host name (#498)

### Description of the change

Introducing `tpl` function on variables related to hostname in `./templates/gitea/ingress.yaml`

### Benefits

The change is intending to support the following syntax in a values.yaml such as:
```
global:
  giteaHostName: "gitea.my-org.com"

ingress:
  enabled: true
  hosts:
    - host: "{{ .Values.global.giteaHostName }}"
      paths:
        - path: /
          pathType: Prefix
  tls:
      - secretName: gitea-tls
        hosts:
          - "{{ .Values.global.giteaHostName }}"
```

### Possible drawbacks

N/A

### Applicable issues

N/A

### Additional information

N/A

Reviewed-on: https://gitea.com/gitea/helm-chart/pulls/498
Reviewed-by: justusbunsi <justusbunsi@noreply.gitea.com>
Co-authored-by: Ceddaerrix <ceddaerrix@noreply.gitea.com>
Co-committed-by: Ceddaerrix <ceddaerrix@noreply.gitea.com>

templates/gitea/ingress.yaml

@@ -28,14 +28,14 @@ spec:
   {{- range .Values.ingress.tls }}
     - hosts:
       {{- range .hosts }}
-        - {{ . | quote }}
+        - {{ tpl . $ | quote }}
       {{- end }}
       secretName: {{ .secretName }}
   {{- end }}
 {{- end }}
   rules:
     {{- range .Values.ingress.hosts }}
-    - host: {{ .host | quote }}
+    - host: {{ tpl .host $ | quote }}
       http:
         paths:
           {{- range .paths }}