[Feature] Follow news channels (#2590)

* initial commit

* Apply suggestions from code review

---------

Co-authored-by: Casmir <68127614+csmir@users.noreply.github.com>

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

@@ -4,6 +4,7 @@ using System.Diagnostics;
 using System.Linq;
 using System.Text;
 using System.Threading.Tasks;
+
 using Model = Discord.API.Channel;
 
 namespace Discord.Rest
@@ -15,7 +16,7 @@ namespace Discord.Rest
     public class RestNewsChannel : RestTextChannel, INewsChannel
     {
         internal RestNewsChannel(BaseDiscordClient discord, IGuild guild, ulong id)
-            :base(discord, guild, id)
+            : base(discord, guild, id)
         {
         }
         internal new static RestNewsChannel Create(BaseDiscordClient discord, IGuild guild, Model model)
@@ -25,5 +26,9 @@ namespace Discord.Rest
             return entity;
         }
         public override int SlowModeInterval => throw new NotSupportedException("News channels do not support Slow Mode.");
+
+        /// <inheritdoc />
+        public Task<ulong> FollowAnnouncementChannelAsync(ulong channelId, RequestOptions options = null)
+            =>  ChannelHelper.FollowAnnouncementChannelAsync(this, channelId, Discord, options);
     }
 }