Support Facebook stickers

external/messenger.py

@@ -502,6 +502,17 @@ class MessengerBridge:
             else:
                 event["text"] += "\nUnhandled attachment: {}".format(at)
 
+        if isinstance(message_object.sticker, Sticker):
+            stk = message_object.sticker
+            event["attachments"].append({
+                "filename": stk.label,
+                "url": stk.url,
+                "image_size": {
+                    "width": stk.width,
+                    "height": stk.height,
+                },
+            })
+
         if thread_type == ThreadType.GROUP:
             event["room"] = thread_id
             self.ensureJoined(author, thread_id)