feature: Add stickers (#1726)

src/Discord.Net.Core/Entities/Messages/IMessage.cs

@@ -164,6 +164,14 @@ namespace Discord
         /// </summary>
         IReadOnlyDictionary<IEmote, ReactionMetadata> Reactions { get; }
 
+        /// <summary>
+        ///     Gets all stickers included in this message.
+        /// </summary>
+        /// <returns>
+        ///     A read-only collection of sticker objects.
+        /// </returns>
+        IReadOnlyCollection<ISticker> Stickers { get; }
+        
         /// <summary>
         ///     Gets the flags related to this message.
         /// </summary>

src/Discord.Net.Core/Entities/Messages/ISticker.cs

@@ -0,0 +1,67 @@
+using System.Collections.Generic;
+
+namespace Discord
+{
+    /// <summary>
+    ///     Represents a discord sticker.
+    /// </summary>
+    public interface ISticker
+    {
+        /// <summary>
+        ///     Gets the ID of this sticker.
+        /// </summary>
+        /// <returns>
+        ///     A snowflake ID associated with this sticker.
+        /// </returns>
+        ulong Id { get; }
+        /// <summary>
+        ///     Gets the ID of the pack of this sticker.
+        /// </summary>
+        /// <returns>
+        ///     A snowflake ID associated with the pack of this sticker.
+        /// </returns>
+        ulong PackId { get; }
+        /// <summary>
+        ///     Gets the name of this sticker.
+        /// </summary>
+        /// <returns>
+        ///     A <see langword="string"/> with the name of this sticker.
+        /// </returns>
+        string Name { get; }
+        /// <summary>
+        ///     Gets the description of this sticker.
+        /// </summary>
+        /// <returns>
+        ///     A <see langword="string"/> with the description of this sticker.
+        /// </returns>
+        string Description { get; }
+        /// <summary>
+        ///     Gets the list of tags of this sticker.
+        /// </summary>
+        /// <returns>
+        ///     A read-only list with the tags of this sticker.
+        /// </returns>
+        IReadOnlyCollection<string> Tags { get; }
+        /// <summary>
+        ///     Gets the asset hash of this sticker.
+        /// </summary>
+        /// <returns>
+        ///     A <see langword="string"/> with the asset hash of this sticker.
+        /// </returns>
+        string Asset { get; }
+        /// <summary>
+        ///     Gets the preview asset hash of this sticker.
+        /// </summary>
+        /// <returns>
+        ///     A <see langword="string"/> with the preview asset hash of this sticker.
+        /// </returns>
+        string PreviewAsset { get; }
+        /// <summary>
+        ///     Gets the format type of this sticker.
+        /// </summary>
+        /// <returns>
+        ///     A <see cref="StickerFormatType"/> with the format type of this sticker.
+        /// </returns>
+        StickerFormatType FormatType { get; }
+    }
+}

src/Discord.Net.Core/Entities/Messages/SticketFormatType.cs

@@ -0,0 +1,15 @@
+namespace Discord
+{
+    /// <summary> Defines the types of formats for stickers. </summary>
+    public enum StickerFormatType
+    {
+        /// <summary> Default value for a sticker format type. </summary>
+        None = 0,
+        /// <summary> The sticker format type is png. </summary>
+        Png = 1,
+        /// <summary> The sticker format type is apng. </summary>
+        Apng = 2,
+        /// <summary> The sticker format type is lottie. </summary>
+        Lottie = 3,
+    }
+}