Add option to not bridge chats with too many members

mautrix_telegram/example-config.yaml

@@ -148,6 +148,10 @@ bridge:
     # will not send any more members.
     # -1 means no limit (which means it's limited to 10000 by the server)
     max_initial_member_sync: 100
+    # Maximum number of participants in chats to bridge. Only applies when the portal is being created.
+    # If there are more members when trying to create a room, the room creation will be cancelled.
+    # -1 means no limit (which means all chats can be bridged)
+    max_member_count: -1
     # Whether or not to sync the member list in channels.
     # If no channel admins have logged into the bridge, the bridge won't be able to sync the member
     # list regardless of this setting.