add (some) sticker support

appservice/discord.py

@@ -34,6 +34,13 @@ class MessageReference:
     guild_id: str
 
 
+@dataclass
+class Sticker:
+    name: str
+    id: str
+    format_type: int
+
+
 @dataclass
 class Typing:
     user_id: str
@@ -114,6 +121,11 @@ class Message:
 
         self.author = User(author) if author else None
 
+        self.stickers = [
+            dict_cls(sticker, Sticker)
+            for sticker in message.get("sticker_items", [])
+        ]
+
 
 class ChannelType:
     GUILD_TEXT = 0

appservice/main.py

@@ -656,6 +656,11 @@ class DiscordClient(Gateway):
         for attachment in message.attachments:
             content += f"\n{attachment['url']}"
 
+        # Append stickers to message.
+        for sticker in message.stickers:
+            if sticker.format_type != 3:  # 3 == Lottie format.
+                content += f"\n{discord.CDN_URL}/stickers/{sticker.id}.png"
+
         return content, emotes