* Type hints: Replace deprecated helpers.typing.EventType with core.Event
* Replace deprecated use of hass.helpers.service.async_register_admin_service
* Typing: Make BaseThermostat generic on the UnderlyingEntity type
* Typing: Change the type of IntervalCaller._interval_sec from int to float
This makes the IntervalCaller class more reusable.
* Keep-alive: Expose UnderlyingSwitch.keep_alive_sec as a HASS Dev Tools attribute
Also improve a keep-alive log message.
* Update Home Assistant dev version in requirements_dev.txt
* Avoid "Error starting FFmpeg" error in VSCode dev container logs
* Add "editor.formatOnSaveMode": "modifications" to .vscode/settings.json
* Add keep_alive feature for directly controlled switches
* Add test cases for the switch keep-alive feature
* Add documentation (readme) and translations for the keep-alive feature