Implement on_published callback for sensor

[blairfancy]

Describe your core improvement

Need a way to know if state of sensor has been published for exemple a on_piblished callback or variable publish_done.

Current limitations

When we build device for low consomption, we use deep sleep feature. But before entering deep sleep we need to be sure that all is published properly to avoid miss.
`

• id: go_sleep
  then:
  - lambda: |-
  id(door).publish_state(id(door).state);
  - delay: 200ms --> this could be replaced by if condition binary_sensor.published: door)
  - deep_sleep.enter:
  id: ds
  sleep_duration: ${sleep_interval}
  `

Technical benefits

Will improve robustness for low consomption application.

Additional context

No response