Add native api note for Home Assistant users

[syssi]

No description provided.

[pmulkins]

api line was not added, nothing to uncomment. Noted it was added to other examples, but not smartshunt-esp8266-example.yaml

# If you use Home Assistant please remove this `mqtt` section and uncomment the `api` component!
# The native API has many advantages over MQTT: https://esphome.io/components/api.html#advantages-over-mqtt
mqtt:
  broker: !secret mqtt_host
  username: !secret mqtt_username
  password: !secret mqtt_password
  id: mqtt_client

[syssi]

@pmulkins Good point!