add runner.docker.services support

[icez]

as per issue #118 I've create this PR on behalf of marcelbrueckner

[riemers]

Nice, if not too much trouble could you add/update example/doc for new folks

[Gerrit91]

It may sounds strange but for me for some reason the task introduced here just hangs forever. No services were defined.

# run with -vvvvvv
...
TASK [riemers.gitlab-runner : conf[2/2]: runner[1/1]: Set additional services] ***
task path: /root/.ansible/roles/riemers.gitlab-runner/tasks/update-config-runner.yml:335

With Ansible:

$ pip freeze
ansible==6.7.0
ansible-core==2.13.7
...

$ ansible --version
ansible [core 2.13.7]
  config file = /etc/ansible/ansible.cfg
  configured module search path = ['/root/.ansible/plugins/modules', '/usr/share/ansible/plugins/modules']
  ansible python module location = /usr/local/lib/python3.11/site-packages/ansible
  ansible collection location = /root/.ansible/collections:/usr/share/ansible/collections
  executable location = /usr/local/bin/ansible
  python version = 3.11.1 (main, Jan 17 2023, 23:45:25) [GCC 10.2.1 20210110]
  jinja version = 3.0.1
  libyaml = True

Running with role release v1.6.50 everything runs just fine. 🙈