Add docker role for making sure Docker is installed

Add a docker role for making sure Docker is installed from the Docker
repositories.
Take the role from the ccchh-ansible repo, provide attribution in the
README and add the relevant license in a new licenses directory.
Modify the role by removing the distribution check and adjusting the
task names to be in line with other task names in this repo.

playbooks/roles/docker/tasks/main/01_repo_setup.yaml

@@ -0,0 +1,15 @@
+- name: Ensure Dockers GPG key is added
+  ansible.builtin.get_url:
+    url: https://download.docker.com/linux/debian/gpg
+    dest: /etc/apt/trusted.gpg.d/docker.asc
+    mode: "0644"
+    owner: root
+    group: root
+  become: true
+
+- name: Ensure Dockers APT repository is added
+  ansible.builtin.apt_repository:
+    repo: "deb [arch=amd64 signed-by=/etc/apt/trusted.gpg.d/docker.asc] https://download.docker.com/linux/debian {{ ansible_distribution_release }} stable"
+    filename: docker
+    state: present
+  become: true