Add voice region to modify voice channels

src/Discord.Net.Core/Entities/Channels/VoiceChannelProperties.cs

@@ -13,5 +13,9 @@ namespace Discord
         ///     Gets or sets the maximum number of users that can be present in a channel, or <c>null</c> if none.
         /// </summary>
         public Optional<int?> UserLimit { get; set; }
+        /// <summary>
+        ///     Gets or sets the channel voice region id, automatic when set to <see langword="null"/>.
+        /// </summary>
+        public Optional<string> RTCRegion { get; set; }
     }
 }

src/Discord.Net.Rest/API/Rest/ModifyVoiceChannelParams.cs

@@ -9,5 +9,7 @@ namespace Discord.API.Rest
         public Optional<int> Bitrate { get; set; }
         [JsonProperty("user_limit")]
         public Optional<int> UserLimit { get; set; }
+        [JsonProperty("rtc_region")]
+        public Optional<string> RTCRegion { get; set; }
     }
 }

src/Discord.Net.Rest/Entities/Channels/ChannelHelper.cs

@@ -77,6 +77,7 @@ namespace Discord.Rest
             {
                 Bitrate = args.Bitrate,
                 Name = args.Name,
+                RTCRegion = args.RTCRegion,
                 Position = args.Position,
                 CategoryId = args.CategoryId,
                 UserLimit = args.UserLimit.IsSpecified ? (args.UserLimit.Value ?? 0) : Optional.Create<int>(),