Add ability to specify parameters on channel creation (#1020)

commit 07bca5b31a3580d55278878eabb56a82973f8c8f
Author: Joe4evr <jii.geugten@gmail.com>
Date:   Fri Apr 6 09:44:50 2018 +0200

    Add ability to specify parameters on channel creation

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

@@ -1,4 +1,4 @@
-#pragma warning disable CS1591
+#pragma warning disable CS1591
 using Newtonsoft.Json;
 
 namespace Discord.API.Rest
@@ -10,9 +10,20 @@ namespace Discord.API.Rest
         public string Name { get; }
         [JsonProperty("type")]
         public ChannelType Type { get; }
+        [JsonProperty("parent_id")]
+        public Optional<ulong?> CategoryId { get; set; }
 
+        //Text channels
+        [JsonProperty("topic")]
+        public Optional<string> Topic { get; set; }
+        [JsonProperty("nsfw")]
+        public Optional<bool> IsNsfw { get; set; }
+
+        //Voice channels
         [JsonProperty("bitrate")]
         public Optional<int> Bitrate { get; set; }
+        [JsonProperty("user_limit")]
+        public Optional<int?> UserLimit { get; set; }
 
         public CreateGuildChannelParams(string name, ChannelType type)
         {