Add MaxBitrate to the interface (#1861)

Co-authored-by: Quin Lynch <49576606+quinchs@users.noreply.github.com>

src/Discord.Net.Core/Entities/Guilds/IGuild.cs

@@ -313,6 +313,13 @@ namespace Discord
         ///     The approximate number of non-offline members in this guild.
         /// </returns>
         int? ApproximatePresenceCount { get; }
+        /// <summary>
+        ///     Gets the max bitrate for voice channels in this guild.
+        /// </summary>
+        /// <returns>
+        ///     A <see cref="int"/> representing the maximum bitrate value allowed by Discord in this guild.
+        /// </returns>
+        int MaxBitrate { get; }
 
         /// <summary>
         ///     Gets the preferred locale of this guild in IETF BCP 47