Add the possibility to pass extra flags to the docker container

roles/matrix-nginx-proxy/templates/systemd/matrix-nginx-proxy.service.j2

@@ -33,6 +33,9 @@ ExecStart=/usr/bin/docker run --rm --name matrix-nginx-proxy \
 			{% for volume in matrix_nginx_proxy_container_additional_volumes %}
 			-v {{ volume.src }}:{{ volume.dst }}:{{ volume.options }} \
 			{% endfor %}
+			{% for arg in matrix_nginx_proxy_container_extra_arguments %}
+			{{ arg }} \
+			{% endfor %}
 			{{ matrix_nginx_proxy_docker_image }}
 
 ExecStop=-/usr/bin/docker kill matrix-nginx-proxy