docker(role): document gVisor issue with user-def. br. and provide help

Document issue with containers on user-defined bridges and using the
gVisor runsc runtime. Also provide a helper resolv.conf as a workaround.

roles/docker/tasks/main/03_docker_config.yaml

@@ -10,3 +10,13 @@
     mode: "0644"
   become: true
   notify: restart the docker service
+
+- name: Ensure helper gVisor resolv.conf is deployed
+  when: docker__gvisor_setup
+  ansible.builtin.copy:
+    src: gvisor-helper-resolv.conf
+    dest: /etc/gvisor-helper-resolv.conf
+    owner: root
+    group: root
+    mode: "0644"
+  become: true