add News channel type

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

@@ -12,6 +12,8 @@ namespace Discord
         /// <summary> The channel is a group channel. </summary>
         Group = 3,
         /// <summary> The channel is a category channel. </summary>
-        Category = 4
+        Category = 4,
+        /// <summary> The channel is a news channel. </summary>
+        News = 5
     }
 }

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

@@ -23,6 +23,7 @@ namespace Discord.Rest
         {
             switch (model.Type)
             {
+                case ChannelType.News:
                 case ChannelType.Text:
                 case ChannelType.Voice:
                     return RestGuildChannel.Create(discord, new RestGuild(discord, model.GuildId.Value), model);

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

@@ -34,6 +34,9 @@ namespace Discord.Rest
         {
             switch (model.Type)
             {
+                case ChannelType.News:
+                    // TODO: create new RestNewsChannel
+                    throw new NotImplementedException();
                 case ChannelType.Text:
                     return RestTextChannel.Create(discord, guild, model);
                 case ChannelType.Voice:

src/Discord.Net.WebSocket/Entities/Channels/SocketGuildChannel.cs

@@ -48,6 +48,9 @@ namespace Discord.WebSocket
         {
             switch (model.Type)
             {
+                case ChannelType.News:
+                    // TODO: create new SocketNewsChannel
+                    throw new NotImplementedException();
                 case ChannelType.Text:
                     return SocketTextChannel.Create(guild, state, model);
                 case ChannelType.Voice: