Add HomeKit support for automations

[schmittx]

Description:

Adds support for automations in HomeKit. Entities will be shown as switches within HomeKit.

Related issue (if applicable): N/A

Pull request in home-assistant.github.io with documentation (if applicable): home-assistant/home-assistant.io#5418

Example entry for configuration.yaml (if applicable):

homekit:
  filter:
    include_domains:
      - automation.garage_door_open

Checklist:

• The code change is tested and works locally.
• Local tests pass with tox. Your PR cannot be merged unless tests pass

If user exposed functionality or configuration variables are added/changed:

• Documentation added/updated in home-assistant.github.io

If the code does not interact with devices:

• Tests have been added to verify that the new code works.

[cdce8p]

Ready once #14446 is merged.