Feature Request: Add the possibility to cast the tts response to media player devices

[lajoshanko]

Since the M5Stack Echo and the ESP32 Box devices have pretty quiet speakers it would be nice to have a feature toggle to cast the voice response the media player devices.

Currently as a workaround the following config can be added to the esphome device config to cast the response to the device.
Where the entity_id is optionally populated from a template select from home assistant.

    - homeassistant.service:
        service: media_player.play_media
        data:
          entity_id: media_player.media_player_entity
          media_content_id: !lambda 'return x;'
          media_content_type: music
          announce: "true" 

Features on the esphome device config page:

1. A feature toggle to turn the casting on/off.
2. A select list of mediaplayers where the state is not off, unavailable, unknown.
3. Maybe a feature toggle to mute the esphome device built-in speaker.