Add Carbon Monoxide HomeKit Sensor

[cdce8p]

Description:

Add support for Carbon Monoxide Sensors in HomeKit as well as small cleanups. The sensor must have the co device_class to be mapped correctly. Either handled through HA or set manually in the customize section. I decided not to add entity_id mapping, since this would create conflicts with co2 sensors.

Feature Request: https://community.home-assistant.io/t/carbon-monoxide-sensor-support/68969

Pull request in home-assistant.github.io with documentation (if applicable): home-assistant/home-assistant.io#6300

Example entry for configuration.yaml (if applicable):

homeassistant:
  customize:
    sensor.carbon_monoxide:
      device_class: 'co'

homekit:

Checklist:

• The code change is tested and works locally.
• Local tests pass with tox. Your PR cannot be merged unless tests pass
• Documentation added/updated in home-assistant.github.io
• Tests have been added to verify that the new code works.