Steps to reproduce.

• Clone repo
• Move example-custom-config/custom_components/mqtt_basic_async to custom_components
• Restart HA
• Add below to configuration.yaml

mqtt_basic_async:
  topic: "home-assistant/mqtt_example"

• Go to Developer Tools and click check configuration to get:

Invalid config for [mqtt_basic_async]: [default_config] is an invalid option for [mqtt_basic_async]. Check: mqtt_basic_async->default_config. (See /config/configuration.yaml, line 29).

which is the 1st line in my configuration.yaml file.

Any ideas? I want to listen to some topics and update some sensors, already have these in sensors.yaml and they work fine, but I would like to develop a more complex integration, and this would be my 1st step :D