Added modifying voice channel password

src/Kook.Net.Core/Entities/Channels/ModifyVoiceChannelProperties.cs

@@ -25,4 +25,9 @@ public class ModifyVoiceChannelProperties : ModifyGuildChannelProperties
     ///     <c>null</c> if not set.
     /// </summary>
     public int? UserLimit { get; set; }
+
+    /// <summary>
+    ///     Gets or sets the password of the channel, or empty string to clear the password; <c>null</c> if not set.
+    /// </summary>
+    public string Password { get; set; }
 }

src/Kook.Net.Rest/API/Rest/ModifyVoiceChannelParams.cs

@@ -12,4 +12,8 @@ internal class ModifyVoiceChannelParams : ModifyGuildChannelParams
 
     [JsonPropertyName("limit_amount")] 
     public int? UserLimit { get; set; }
+
+    [JsonPropertyName("password")]
+    [JsonIgnore(Condition = JsonIgnoreCondition.WhenWritingNull)]
+    public string Password { get; set; }
 }

src/Kook.Net.Rest/Entities/Channels/ChannelHelper.cs

@@ -63,7 +63,8 @@ public static async Task<Model> ModifyAsync(IVoiceChannel channel, BaseKookClien
             Position = args.Position,
             CategoryId = args.CategoryId,
             VoiceQuality = args.VoiceQuality,
-            UserLimit = args.UserLimit
+            UserLimit = args.UserLimit,
+            Password = args.Password
         };
         return await client.ApiClient.ModifyGuildChannelAsync(channel.Id, apiArgs, options).ConfigureAwait(false);
     }