Added some XML doc comments.

DiscordClient/DiscordUserClient.cs

@@ -54,6 +54,15 @@ public class DiscordUserClient
         return await _httpClient.DeleteAsync(url);
     }
 
+    /// <summary>
+    /// This method returns some of most recent messages, sent to a guild.
+    /// </summary>
+    /// <param name="guildId">Guild ID from which we're gathering messages.</param>
+    /// <param name="authorId">
+    /// Optional author ID. If specified, gather only
+    /// recent messages from this particular author.
+    /// </param>
+    /// <returns></returns>
     public async Task<GuildMessageSearchResponse?> SearchGuildMessages(
         string guildId,
         string? authorId = null