move generated stubs to separate directory, too messty

django-stubs-generated/core/mail/backends/dummy.pyi

@@ -0,0 +1,9 @@
+from typing import Any, List, Optional
+
+from django.core.mail.backends.base import BaseEmailBackend
+from django.core.mail.message import EmailMessage
+
+
+class EmailBackend(BaseEmailBackend):
+    fail_silently: bool
+    def send_messages(self, email_messages: List[EmailMessage]) -> int: ...