Max/Min length fields for ApplicationCommandOption (#2379)

* implement max/min length fields for ApplicationCommandOption

* fix badly formed xml comments

src/Discord.Net.WebSocket/Entities/Interaction/SocketBaseCommand/SocketApplicationCommandOption.cs

@@ -33,6 +33,12 @@ namespace Discord.WebSocket
         /// <inheritdoc/>
         public double? MaxValue { get; private set; }
 
+        /// <inheritdoc/>
+        public int? MinLength { get; private set; }
+
+        /// <inheritdoc/>
+        public int? MaxLength { get; private set; }
+
         /// <summary>
         ///     Gets a collection of choices for the user to pick from.
         /// </summary>
@@ -72,6 +78,9 @@ namespace Discord.WebSocket
 
             IsAutocomplete = model.Autocomplete.ToNullable();
 
+            MinLength = model.MinLength.ToNullable();
+            MaxLength = model.MaxLength.ToNullable();
+
             Choices = model.Choices.IsSpecified
                 ? model.Choices.Value.Select(SocketApplicationCommandChoice.Create).ToImmutableArray()
                 : ImmutableArray.Create<SocketApplicationCommandChoice>();