Add a button to trigger stt-start

[trfife]

Sometimes I'd like to be able to do follow-up conversations but don't want to say the wakeword so it would be awesome to skip that step with a button.

Example:

User: Ok Nabu -> turn on the light
LLM: Based on the device you are speaking to I see two lights in this room, 1. lamp, 2. fan light or 3. all lights. Please say the number of your choice.
Trigger stt listening
User: 2 please
LLM: Great, I will turn on the fan light
Trigger: Fan light on