add (overwrite with) mypy stubs, if available

stdlib/3/socketserver.pyi

@@ -0,0 +1,15 @@
+# Stubs for socketserver
+
+# NOTE: These are incomplete!
+
+from typing import Tuple
+
+class BaseRequestHandler(): ...
+
+class TCPServer():
+    def __init__(
+        self,
+        server_address: Tuple[str, int],
+        request_handler: BaseRequestHandler,
+        bind_and_activate: bool = True,
+    ) -> None: ...