UNKNOWN_ERROR when browser doesn't support WebRTC

### Discussed in https://github.com/cinnyapp/cinny/discussions/2805 So the cause of this discussion wasn't a Cinny issue. However, Cinny handled it by displaying `UNKNOWN_ERROR` instead of anything more specific, which is unhelpful. This lead to a user spending over a week with two additional creatures trying to figure this out, which easily could have caused others to just use a different client. #### Expected behavior Cinny would display a message about needing to enable WebRTC.