Add support for persistent snapshot by using custom characteristic support by Home+ app
The [Home+ app](https://apps.apple.com/de/app/home-5/id995994352) sold in the app store has support for persistent snapshots of camera pictures.
See details here: https://github.com/brutella/hkcam/blob/master/SNAPSHOTS.md
It is realized by a custom HomeKit characteristic. 

The snapshots are stored locally on the camera. And the Home+ app provides a way of showing a list of those snapshots.
See the description of the feature here on this page: https://hochgatterer.me/hkcam/

Would it be possible to implement support for this custom HomeKit characteristic into this plugin as well?
It is somehow a good alternative to Homekit Secure Video as everything is stored locally.
Maybe one could convince other app developers to support this characteristic too. (ok, maybe not Apple themselves.)
