Support watchOS in the companion app

[mKeRix]

We should take a look at whether the APIs used by the companion app are also available in watchOS - and if they are we should see if we can use that to extend companion app support to the Watch. During the initial implementation a bunch of posts suggested that this isn't possible, but reading the docs now makes it seem like it could be possible now.

[mKeRix]

I dug around in the docs some more - the concept that room-assistant uses now won't work 1:1 for the watch, since it doesn't allow apps to register GATT services. However, in theory you should still be able to do some detection magic by only advertising and using the "overflow" area as an identifier.

This would have to be a breaking change in how room-assistant works and entails some changes on both ends. Has its own drawbacks, but also the huge plus that direct connections to the device wouldn't be needed for this anymore. I would like to at least give this a shot in a PoC sometime.