docker_containers inventory: fix wrong default mentioned in docs, add fallback example (#194)

* Fix wrong default mentioned in docs.

* Add fallback example.

plugins/inventory/docker_containers.py

@@ -38,11 +38,11 @@ options:
     connection_type:
         description:
             - Which connection type to use the containers.
-            - Default is to use SSH (C(ssh)). For this, the options I(default_ip) and
-              I(private_ssh_port) are used.
+            - One way to connect to containers is to use SSH (C(ssh)). For this, the options I(default_ip) and
+              I(private_ssh_port) are used. This requires that a SSH daemon is running inside the containers.
             - Alternatively, C(docker-cli) selects the
               R(docker connection plugin,ansible_collections.community.docker.docker_connection),
-              and C(docker-api) selects the
+              and C(docker-api) (default) selects the
               R(docker_api connection plugin,ansible_collections.community.docker.docker_api_connection).
             - When C(docker-api) is used, all Docker daemon configuration values are passed from the inventory plugin
               to the connection plugin. This can be controlled with I(configure_docker_daemon).
@@ -138,6 +138,14 @@ keyed_groups:
   # Add Linux hosts to an os_linux group
   - prefix: os
     key: docker_platform
+
+# Example using SSH connection with an explicit fallback for when port 22 hasn't been
+# exported: use container name as ansible_ssh_host and 22 as ansible_ssh_port
+plugin: community.docker.docker_containers
+connection_type: ssh
+compose:
+  ansible_ssh_host: ansible_ssh_host | default(docker_name[1:], true)
+  ansible_ssh_port: ansible_ssh_port | default(22, true)
 '''
 
 import re