feat(voiceState): add self_video property (#4346)

src/structures/VoiceState.js

@@ -48,6 +48,11 @@ class VoiceState extends Base {
      * @type {?boolean}
      */
     this.selfMute = data.self_mute;
+    /**
+     * Whether this member's camera is enabled
+     * @type {boolean}
+     */
+    this.selfVideo = data.self_video;
     /**
      * The session ID of this member's connection
      * @type {?string}