Add missing typing to .interested

Author: Middledot

discord/scheduled_events.py

@@ -218,7 +218,7 @@ def created_at(self) -> datetime.datetime:
         return utils.snowflake_time(self.id)
 
     @property
-    def interested(self):
+    def interested(self) -> Optional[int]:
         """An alias to :attr:`.subscriber_count`"""
         return self.subscriber_count