Support on_command_type from MQTT Lights

[AdamN1]

Add support for brightness change without payload 'on' command. We can support this by userconfig variable from the config.yaml so anyone can choose what prefer.

on_command_type description

Defines when on the payload_on is sent. Using last (the default) will send any style (brightness, color, etc) topics first and then a payload_on to the command_topic. Using first will send the payload_on and then any style topics. Using brightness will only send brightness commands instead of the payload_on to turn the light on.

from: https://www.home-assistant.io/integrations/light.mqtt/#on_command_type

[dgomes]

how does this affect a dali2mqtt ?