Missing voice state properties

Created by: JackSteel97

Summary

Feature addition: self_stream and self_video VoiceState properties

Details

The current DiscordVoiceState object is missing corresponding properties for the self_stream and self_video flags returned by the Discord API (see: https://discord.com/developers/docs/resources/voice#voice-state-object-voice-state-structure). These would be a useful addition to the voice state update, and I imagine relatively easy to implement as they are simply new properties on the Library end already returned by an existing endpoint.