tweak(scripts/ansible): add var tinedockercompose_dns

see https://docs.docker.com/compose/compose-file/05-services/#dns

Author: pschuele

scripts/ansible/roles/tinedockercompose/templates/docker-compose.yml.j2

@@ -73,6 +73,9 @@ services:
     extra_hosts:
       - "{{ tinedockercompose_extra_hosts }}"
 {% endif %}
+{% if tinedockercompose_dns is defined %}
+    dns: "{{ tinedockercompose_dns }}"
+{% endif %}
 {% if tinedockercompose_traefik_host is defined %}
     ### for traefik support (see https://doc.traefik.io/traefik/providers/docker/)
     labels: