Add comment explaining why this step goes here

roles/matrix-client-hydrogen/tasks/setup.yml

@@ -53,6 +53,8 @@
     - {src: "{{ role_path }}/templates/nginx.conf.j2", name: "nginx.conf"}
   when: "matrix_client_hydrogen_enabled|bool and item.src is not none"
 
+# This step MUST come after the steps to install the configuration files because the config files
+# are currently only read at build time, not at run time like most other components in the playbook
 - name: Ensure Hydrogen Docker image is built
   docker_image:
     name: "{{ matrix_client_hydrogen_docker_image }}"