Google-nest-sdm

What's Changed
* New Event manager API for caching and pre-fetching media clips for all camera types

**Full Changelog**: https://github.com/allenporter/python-google-nest-sdm/compare/0.3.9...0.4.0

- Can now create and delete subscriptions

- Support for camera clip previews, an mp4 with 10 frame video for new battery cameras

- Battery camera support and WebRTC

- Additional static typing fixes

- Make some runtime type assertions more forgiving