fix: strip line break in message validity check (#11)

Author: callebtc

nostr/relay.py

@@ -80,6 +80,7 @@ def _on_error(self, class_obj, error):
         pass
 
     def _is_valid_message(self, message: str) -> bool:
+        message = message.strip("\n")
         if not message or message[0] != '[' or message[-1] != ']':
             return False